(^ 


.^^ 

^ 


Air^  Water^  and  Food 


FROM  A  SANITARY  STANDPOINT 


BY 

ALPHEUS  G.  WOODMAN  and  JOHN  F.  NORTON 

Associate  Professor  of  Assistant  Professor  of 

Food  A  nalysis  Chetnistry  of  Sanitation 

MASSACHl,'SKTTS  INSTITUTE  OF  TECHNOLOGY 


"  These  cannot  be  taken  as  sufficient ...  in  these  times  when 
every  word  spoken  finds  at  once  a  reidy  doubter,  if  not  an  opponent. 
They  are,  however,  specimens,  and  will  serve  to  make  comparisons 
in  time  to  come."  —  Angus  Smith. 

"  The  ideal  scientific  mind,  therefore,  must  always  be  held  in  a 
state  of  balance  which  the  slightest  new  evidence  may  change  in  one 
direction  or  another.  It  is  in  a  constant  state  of  skepticism,  know- 
ing full  well  that  nothing  is  certain."  — Henry  A.  RowIiANO.-i    -• 


FOURTH  EDITION,   RRVI5Eri''A^D>,J^>f:iVJiiT'tMN' 

TOTAL  ISSUE  FIVE ^y'ltofu'sAigif.  .'     ;'.*,*>! 


NEW   YORK 

JOHN    WILEY    &    SONS,    Inc. 

London:    CHAPMAN   &   HALL,   Limited 

1914 


Copyright,  1900,  1904,  1909 

BY 

ELLEN  H.  RICHARDS  and  ALPHEUS  G.  WOODMAN 
Copyright,  19 14 

BY 

ALPHEUS  G.  WOODMAN  and  JOHN  F.  NORTON 


Stanbopc  jpress 

F.    H.GILSON    COMPANY 
BOSTON,  U.S.A. 


^/3 


PREFACE 


Since  the  last  edition  (1909)  of  Air,  Water,  and  Food  was 
published  there  have  been  distinct  advances  in  analytical  meth- 
ods, and  a  changed  point  of  view  has  brought  about  a  somewhat 
different  interpretation  of  results.  This  is  particularly  true 
with  regard  to  the  relation  of  air  to  health  and  comfort.  At  the 
present  time  the  subject  is  still  in  a  somewhat  transitory  state. 
In  order  that  the  book  might  remain  useful  it  seemed  necessary 
to  make  a  careful  revision  of  the  whole. 

The  death  of  one  of  the  authors,  Mrs.  Ellen  H.  Richards, 
made  a  change  in  authorship  necessary.  We  are  indebted  to 
Prof.  R.  H.  Richards  for  permission  to  use  any  material  from 
the  former  edition.  While  realizing  that  the  book  was  first 
written  from  a  "missionary"  standpoint  (Mrs.  Richards' 
strong  point),  it  actually  has  been  used  mainly  for  college  and 
technical  school  teaching;  consequently  the  character  of  part  of 
the  general  discussion  has  been  considerably  changed. 

All  of  the  discussion  on  air  and  water  has  been  completely 
rewritten,  as  has  the  section  on  milk,  the  older  methods  revised, 
and  numerous  additions,  to  correspond  with  the  latest  practice, 
made.  As  in  previous  editions,  these  discussions  are  intended 
to  be  essentially  elementary  rather  than  exhaustive. 

A.    G.   W. 
J.   F.   N. 

Boston,  July,  1914. 


2061665 


CONTENTS 


Chapter  Page 

I.  Three  Essentials  of  Human  Existence i 

II.   Air  and  Health q 

HI.   Air:   Analytical  Methods 21 

IV.   Water:   Its  Relation  to  Health,  Its  Source  and  Properties..  43 

V.   Safe  Water  and  the  Interpretation  of  Analyses 56 

VI.   Water:  Analytical  Methods 69 

VII.   Food  in  Relation  to  Human  Life,  Definition,  Sources,  Classes, 

Dietaries m 

VIII.   Adulteration  and  Sophistication  of  Food  Materials 124 

IX.   Analytical  Methods 135 

Appendices 208 

Bibliogr.'Vphy 228 


AIR,  WATER,  AND   FOOD 


CHAPTER   I 

THREE   ESSENTIALS   OF   HUMAN   EXISTENCE 

Air,  water,  and  food  are  three  essentials  for  healthful  human 
life.  Chemical  Analysis  deals  with  these  three  commodities  in 
their  relation  to  the  needs  of  daily  existence:  first,  as  to  their 
normal  composition;  second,  as  to  natural  variations  from  the 
normal;  third,  as  to  artificial  variations  —  those  produced 
directly  by  human  agency  with  benevolent  intention,  or  result- 
ing from  carelessness  or  cupidity.  A  large  portion  of  the  prob- 
lems of  public  health  come  under  these  heads,  and  a  discussion 
of  them  in  the  broadest  sense  includes  a  consideration  of  engi- 
neering questions  and  of  municipal  finances.  This,  however,  is 
beyond  the  scope  of  the  present  work. 

The  following  pages  will  deal  chiefly  with  such  portions  of 
the  Chemistry  of  Sanitation  as  come  directly  under  indi\'idual 
control,  or  which  require  the  education  of  individuals  in  order 
to  make  up  the  mass  of  public  opinion  which  shall  support  the 
city  or  state  in  carrying  out  sanitary  measures. 

A  notable  interest  in  the  subject  of  individual  health  as  a 
means  of  securing  the  highest  individual  capacity  both  for 
work  and  for  pleasure  is  being  aroused  as  the  application  of 
the  principles  governing  the  evolutionary  progress  of  other 
forms  of  Uving  matter  is  seen  to  extend  to  mankind. 

Will  power  may  guide  human  forces  in  most  economical 
ways,  and  may  concentrate  energy  upon  a  focal  point  so  as 
to  seem  to  accomphsh  superhuman  feats,  but  it  cannot  create 
force  out  of  nothing.     There  is  a  law  of  conservation  of  human 


2  AIR,   WATER,   AND    FOOD 

energy.  The  human  body,  in  order  to  carry  on  all  its  functions 
to  the  best  advantage,  especially  those  of  the  highest  thought 
for  the  longest  time,  must  be  placed  under  the  best  conditions 
and  must  be  supplied  with  clean  air,  safe  water,  and  good  food, 
and  must  be  able  to  appropriate  them  to  its  use.  The  day  is 
not  far  distant  when  a  city  will  be  held  as  responsible  for  the 
purity  of  the  air  in  its  schoolhouses,  the  cleanliness  of  the  water 
in  its  reservoirs,  and  the  rehability  of  the  food  sold  in  its  markets 
as  it  now  is  for  the  condition  of  its  streets  and  bridges.  Nor 
will  the  years  be  many  before  educational  institutions  will  be 
held  as  responsible  for  the  condition  of  the  bodies  as  of  the 
minds  of  the  pupils  committed  to  their  care;  when  a  chair  of 
Sanitary  Science  will  be  considered  as  important  as  a  chair 
of  Greek  or  Mathematics;  when  the  competency  of  the  food- 
purveyor  will  have  as  much  weight  with  intelligent  patrons  as 
the  scholarly  reputation  of  any  member  of  the  Faculty.  Within 
a  still  shorter  time  will  catalogues  call  the  attention  of  the  inter- 
ested public  to  the  ventilation  of  college  halls  and  dormitories, 
as  well  as  to  the  exterior  appearance  and  location. 

These  results  can  be  brought  about  only  when  the  students 
themselves  appreciate  the  possibilities  of  increased  mental  produc- 
tion under  conditions  of  decreased  friction,  such  as  can  be  found 
only  when  the  requirements  of  health  are  perfectly  fulfilled. 

Of  the  three  essentials,  air  may  well  be  considered  first,  al- 
though its  ofiice  is  to  convert  food  already  taken  into  heat  and 
energy.  Its  exclusion  only  for  a  few  minutes  causes  death,  and 
in  quantity  used  it  far  exceeds  the  other  two.  Again,  so  im- 
portant is  the  action  of  air  that  the  quality  of  food  is  of  far  less 
consequence  when  abundant  oxygen  is  present,  as  in  pure  air, 
than  when  it  is  present  in  lessened  quantity,  as  in  air  vitiated 
by  foreign  substances. 

Individual  habit  has  much  to  do  with  the  appreciation  of 
good  air,  and  as  our  knowledge  of  the  value  of  an  abundance  of 
this  substance  in  securing  great  efficiency  in  the  human  being 
increases,  we  shall  be  led  to  attach  more  importance  to  the 
sufiSciency  of  the  supply. 


THREE   ESSENTIALS   OF   HUMAN   EXISTENCE  3 

In  northern  climates  air  is  not  free  to  all  in  the  sense  of  cost- 
ing nothing,  for  the  coming  of  fresh  air  into  the  house  means 
an  accompaniment  of  cold  which  must  be  counteracted  by  the 
consumption  of  fuel.  A  mistaken  idea  of  economy  leads  house- 
holders, school  boards,  and  college  trustees  to  limit  the  size  of 
the  air-ducts  as  well  as  of  the  rooms.  It  is  therefore  necessary 
to  emphasize  the  facts  which  science  has  fully  established,  in 
order  to  secure  the  survival  of  the  fittest  of  the  race  under  the 
present  pressure  of  economic  conditions,  which  take  so  little 
account  of  the  highest  welfare  of  the  human  machine. 

Air,  water,  and  soil  are  the  common  possessions  of  man- 
kind. It  is  impossible  for  man  to  use  either  selfishly  without 
injury  to  his  neighbor  and  without  squandering  his  inheritance. 
Primitive  man  could  leave  a  given  spot  when  the  soil  became 
offensive,  and  neighbors  were  then  too  few  to  require  con- 
sideration; but  neither  man  nor  beast  could  with  impunity  foul 
the  stream  for  his  neighbor  who  had  rights  below  him.  The 
soil  is  permanent;  one  knows  where  to  look  for  it  and  its  pollu- 
tion. Air  is  abundant  and  is  kept  in  constant  motion  by  forces 
of  nature  beyond  human  control,  so  that,  save  in  the  neighbor- 
hood of  an  exceptionally  offensive  factory,  man  does  not  often 
foul  the  free  air  of  heaven ;  it  is  only  when  he  confines  it  within 
unwonted  bounds  that  it  becomes  a  menace. 

Water  is  the  next  precious  commodity  of  the  three.  With- 
out it  man  dies  in  a  few  days;  without  it  the  soil  is  barren; 
without  it  air  in  motion  parches  all  vegetation  and  carries 
clouds  of  dust  particles;  without  it  there  is  no  Hfe.  As  popu- 
lation increases  it  becomes  necessary  to  collect  as  much  of  the 
rainfall  as  possible,  to  store  it  until  needed,  and  to  use  it  with 
discretion.  After  use  it  is  often  loaded  with  impurities  and  sent 
to  deal  death  and  destruction  to  those  who  require  it  later,  and 
yet,  in  nature's  plan,  it  is  the  carrier  of  the  world,  and  rightly 
treated  and  carefully  husbanded  there  is  enough  for  the  needs  of 
all.  Its  presence  or  absence  has  been  the  controlling  force  in 
determining  the  habitations  of  men.  In  its  ofl&ce  of  carrier  it 
not  only  brings  nourishment  in  solution  to  the  tissues  of  the 


4  AIR,   WATER,   AND    FOOD 

human  body,  but  also  carries  away  the  refuse  material.  It  is  a 
cardinal  principle  in  all  sanitary  reforms  to  get  rid  of  that  which 
is  useless  as  soon  as  possible.  Too  little  water  allows  accumu- 
lation of  waste  material  and  a  clogging  of  the  bodily  drainage 
system. 

The  average  quantity  needed  daily  by  the  human  body  is 
about  three  quarts.  Of  this  a  greater  or  less  proportion  is  taken 
in  food,  so  that  at  times  only  from  a  pint  to  a  quart  need  be 
taken  in  the  form  of  water  as  such. 

Next  in  importance  to  quantity  is  the  quality,  dependent 
somewhat  upon  the  uses  to  which  it  is  to  be  put.  As  a  rule, 
the  moderately  soft  waters  are  the  best  for  any  purpose.  For 
drinking  purposes  water  must  be  free  from  dangers  to  health  in 
the  way  of  poisonous  metals,  decomposing  matters,  and  disease- 
germs.  For  domestic  use  economy  requires  that  it  should  not 
decompose  too  much  soap.  Manufacturing  interests  require 
that  it  should  not  give  too  much  scale  to  boilers;  for  agriculture 
there  should  not  be  too  much  alkali. 

From  the  nature  of  things,  no  one  family  or  city  can  have 
sole  control  of  a  given  body  of  water.  Those  on  the  highlands 
may  have  the  first  use  of  the  water,  which  then  percolates  to  a 
lower  level  and  is  used  by  the  people  on  the  slopes  over  and 
over  before  it  reaches  the  sea  to  start  again  on  its  cycle  of  vapor, 
cloud  and  rain,  brook  and  river.  Although  receiving  impurities 
each  time,  there  are  many  beneficent  influences  at  work  to 
overcome  the  evils  resulting  from  this  repeated  use.  That 
which  is  dissolved  from  one  portion  of  earth  may  be  deposited 
on  another.  As  the  plant  is  the  scavenger  of  the  air,  withdraw- 
ing the  carbon  dioxide  with  which  it  would  otherwise  become 
loaded,  so  the  water  has  also  its  plant  hfe,  purifying  it  and 
withdrawing  that  which  would  otherwise  soon  render  it  unfit 
for  any  use. 

Pure  water  is  found  only  in  the  chemical  laboratory;  the  most 
that  can  be  hoped  for  is  that  human  beings  may  secure  for  them- 
selves water  which  is  safe  to  drink,  which  will  not  impair  the 
efficiency  of  the  human  machine. 


THREE   ESSENTIALS   OF   HUMAN   EXISTENCE  5 

The  importance  of  the  third  essential  for  human  life,  food, 
and  the  close  interdependence  of  all  three,  may  be  clearly  shown. 
Of  little  use  is  it  to  provide  pure  air  and  clean  water  if  the  sub- 
stances eaten  are  not  capable  of  combining  with  the  oxygen  of 
the  air  or  of  being  dissolved  in  the  water  or  the  digestive  juices; 
of  less  use  still  is  it  to  partake  of  substances  which  act  as  irri- 
tants and  poisons  on  the  tissues  which  they  should  nourish,  and 
thus  prevent  healthful  metabolism  and  respiratory  exchange. 

And  yet  a  large  majority  of  those  who  have  acquired  some 
notion  of  the  meaning  and  importance  of  pure  air  and  are  be- 
ginning to  consider  it  worth  while  to  strive  for  clean  water  pay 
not  the  least  attention  to  the  sanitary  qualities  of  food;  the 
palatable  and  aesthetic  aspects  only  appeal  to  them. 

Steam-power  is  produced  by  the  combustion  of  coal  or  oil. 
Human  force  is  derived  by  releasing  the  stored  energy  of  the 
food  in  the  body.  The  delicately  balanced  mechanism  of  the 
human  body  suffers  even  more  from  friction  than  the  most 
sensitive  machine,  and  the  greatest  loss  of  potential  human 
energy  occurs  through  ignorance,  carelessness,  and  reckless  dis- 
regard of  nature's  laws  in  regard  to  food. 

It  is  necessary  to  know,  first,  what  is  the  normal  compo- 
sition of  a  given  food-material.  This  is  found  by  analyses  of 
many  typical  samples.  Second,  is  the  sample  under  consider- 
ation normal?  To  answer  this  requires  an  analysis  of  it,  and  a 
comparison  of  the  results  with  standards.  If  it  is  not  normal, 
in  what  way  does  it  depart  from  the  standard  both  in  health- 
fulness  and  in  quality?  Third,  if  a  food-substance  is  normal, 
what  are  its  valuable  ingredients  and  in  what  proportions  are 
they  to  be  used  in  the  daily  diet? 

In  regard  to  meat,  milk,  and  fish,  the  sanitary  aspect  for  the 
chemist  resolves  itself  into  two  questions:  Is  the  substance  so 
changed  as  to  become  a  possible  source  of  poisonous  products? 
Or  has  anything  in  the  nature  of  a  preservative  been  added  to 
it?     If  so,  is  it  of  a  nature  injurious  to  man? 

There  is,  however,  a  great  range  of  quality  in  some  of  the 
most  abundant  foodstuft's,  such  as  the  cereals,  especially  in  the 


AIR,   WATER,   AND    FOOD 


nitrogen  content.  This  is  most  important  to  the  vegetarian 
and  to  institutions  where  economy  must  be  practiced.  The  fol- 
lowing variations  in  the  composition  of  leading  cereals  will 
illustrate: 


Water. 


Nitro- 
genous 
substance. 


Crude 
fat. 


Carbo- 
hydrates. 


Fibre. 


Ash. 


Oats,  maximum 

Oats,  minimum 

Oats,  American  hulled 

Corn,  maximum 

Corn,  minimum 


20.80 
6.  21 


22.  20 
4.68 


18.84 

6.00 

13-57 

14-31 

5-55 


10.65 
2.  II 
7.68 
8.87 
1-73 


.63 

20. 

.69 

4- 

•37 

I . 

.08 

7- 

■75 

0. 

.08 

■45 

■30 

71 

■99 


8.64 

1-34 
2.03 

3-93 
0.82 


One  sample  of  wheat  flour  may  contain  14  per  cent  of  nitro- 
genous substance,  another  may  yield  only  9.  A  day's  ration, 
500  grams,  will  give  70  grams  of  gluten,  etc.,  in  the  one  case 
and  only  45  in  the  other.  This  difference  of  25  grams  would  be 
a  serious  factor  in  the  dietary  of  an  institution  where  little  ad- 
ditional protein  is  given,  and  it  alone  might  be  the  cause  of 
dangerous  under-nutrition. 

The  next  step  would  naturally  be  to  determine  how  definitely 
these  varying  percentages  mean  varying  nutrition.  To  this  end 
a  study  of  vegetable  nitrogenous  products  in  their  combination 
or  contact  with  cellulose,  starch,  and  mineral  matter  is  needed. 
Much  work  remains  to  be  done  before  these  questions  can  be 
even  approximately  answered. 

At  the  low  cost  of  one  cent  a  pound,  common  vegetables 
yield  only  about  one-fifth  as  much  nutriment  as  one  cent's 
worth  of  flour,  yet  they  contain  essential  elements  and  deserve 
to  be  carefully  studied. 

The  sanitary  aspect  of  food  demands  a  study  of  normal  food 
and  food  value  even  more  than  of  adulterants  or  of  poisonous 
food,  ptomaines  and  toxines.  The  cultivation  of  intelligent 
public  opinion  is  most  important,  and  each  student  should  go 
out  from  a  sanitary  laboratory  a  missionary  to  his  fellow  men. 
That  is,  the  office  of  a  laboratory  of  sanitary  chemistry  should 
be  so  to  diffuse  knowledge  as  to  make  it  impossible  for  educated 


THREE   ESSENTIALS   OF   HUMAN   EXISTENCE  ^ 

people  to  be  deluded  by  the  representations  of  unprincipled 
dealers.  Freedom  from  superstition  is  just  as  important  in 
this  as  in  the  domain  of  astronomy  or  physics.  So  long  as 
chemists  are  employed  by  manufacturing  concerns  in  making 
adulterated  and  fraudulent  foodstuffs,  so  long  must  other 
chemists  be  employed  in  protecting  the  people  until  the  public 
in  general  becomes  wiser.  A  part  of  the  common  knowledge  of 
the  race  should  be  the  essentials  of  healthful  living,  in  order  that 
the  full  measure  of  human  progress  may  be  enjoyed. 

There  is  needed  a  greater  respect  for  food  and  its  functions 
in  the  human  body,  a  better  knowledge  of  its  effect  on  the 
daily  output  of  energy,  its  absolute  relations  to  health  and  life, 
and  the  enjoyment  of  the  same.  The  familiarity  with  these 
facts  which  is  given  by  a  few  hours'  work  in  the  laboratory  will 
make  a  lasting  impression  and  will  enable  the  student  to  benefit 
his  whole  life,  even  if  he  never  uses  it  professionally.  It  is 
purely  scientific  knowledge,  just  as  much  as  that  derived  from  a 
study  of  the  phases  of  the  moon  or  the  formulas  of  integration. 

The  variety  of  operations  in  such  work,  calling  for  great 
diversity  of  apparatus  and  methods,  is  an  educational  factor 
not  to  be  overlooked  in  laboratory  training. 

For  all  detailed  discussions  and  methods  the  reader  is  re- 
ferred to  such  works  as  those  of  Wiley,  Allen,  Leach,  etc.,  but 
for  the  student  who  needs  to  study,  as  a  part  of  general  educa- 
tion, only  typical  substances,  and  such  methods  as  can  be 
carried  out  within  the  limits  of  laboratory  exercises  in  a  col- 
lege curriculum,  the  following  pages  are  written.  Not  enough 
is  given  to  frighten  or  discourage  the  student,  but  enough,  it 
is  hoped,  to  arouse  an  interest  which  will  impel  him  at  every 
subsequent  opportunity  to  seek  for  more  and  wider  knowledge. 

Food  is  too  generally  regarded  as  a  private,  individual  matter 
rather  than  as  a  branch  of  social  economy;  it  is,  however,  too 
fundamental  to  the  welfare  of  the  race  to  be  neglected.  Society, 
in  order  to  protect  itself,  must  take  cognizance  of  the  questions 
relative  to  food  and  nutrition. 

Formerly  each  race  adapted  itself  to  its  environment  and 


8  AIR,   WATER,   AND    FOOD 

trained  its  digestion  in  accordance  with  the  available  food 
supply.  In  America  to-day  the  question  is  not  how  to  get 
food  enough,  but  how  to  choose  from  the  bewildering  variety 
offered  that  which  shall  best  promote  the  health  and  develop 
the  powers  of  the  human  being,  and,  what  is  of  equal  impor- 
tance, how  to  avoid  over-indulgence,  which  weakens  the  moral 
fibre  and  lessens  mental  and  physical  efficiency.  In  spite  of  all 
preaching,  few  really  beHeve  that  plain  living  goes  with  high 
thinking.  Professor  Patten  says  that  the  ideal  of  health  is  to 
obtain  complete  nutrition.  Over-nutrition  as  well  as  under- 
nutrition weakens  the  body  and  subjects  it  to  evils  that  make 
it  incapable  of  survival. 

No  other  form  of  social  service  will  give  so  full  a  return  for 
effort  expended  as  the  help  given  toward  better  diet  for  children 
and  students.  Fortunately  help  is  coming  fast.  The  United 
States  Government  is  giving  much  study  to  food  problems,  and 
by  publications  is  making  available  the  work  of  other  countries. 
The  later  bulletins  Hsted  in  the  bibliography  at  the  end  of  this 
volume  are  especially  valuable.  What  is  now  needed  is  a  gen- 
eral recognition  of  the  importance  of  the  subject. 


CHAPTER  II 


AIR   AND   HEALTH 


The  air  we  breathe  is  a  mixture  of  various  gaseous  substances 
containing  more  or  less  finely  divided  solid  particles.  What 
may  be  called  "pure"  air  contains  20.938  per  cent  *  by  volume 
of  oxygen,  0.031  per  cent  of  carbon  dioxide,  78.09  per  cent  of 
nitrogen,  0.94  per  cent  of  argon  and  other  rare  gases  belonging 
to  the  argon  group. 

All  the  air  with  which  we  actually  have  to  deal  contains  also 
varying  amounts  of  moisture,  expressed  in  terms  of  "relative 
humidity."  Air  at  a  low  temperature  can  hold  much  less 
moisture  than  at  a  high  temperature.  For  example,  one  cubic 
foot  of  air  at  20°  F.  will  hold  1.235  grains  of  water  vapor,  while 
at  70°  7.98  grains  will  be  held.  The  relative  humidity  is  the 
ratio  of  the  amount  of  moisture  which  the  air  actually  contains 
to  the  amount  which  it  could  hold  at  the  same  temperature  if 
completely  saturated.  As  water  vapor  is  lighter  than  dry  air, 
the  higher  the  humidity  the  less  will  a  given  volume  of  air 
weigh.  This  effect  is  familiar  in  the  action  of  a  barometer 
which  falls  on  the  approach  of  a  rain  storm,  —  the  reading 
on  such  an  instrument  being  dependent  on  the  weight  of  air 
above  it. 

Besides  moisture,  the  air  in  cities  may  contain  a  variety  of 
substances  such  as  ammonia,  sulphur  dioxide,  sulphur  trioxide, 
etc.,  and  almost  always  dust,  bacteria,  yeasts,  and  molds. 
Samples  of  air  f  taken  in  the  down  town  districts  of  New  York 
and  Boston  showed  at  the  street  level  numbers  of  dust  particles 
per  cubic  foot  of  air  varying  from  170,000  to  500,000,  the  num- 

*  Benedict,  Composition  of  the  Atmosphere.  Carnegie  Institution,  Publication 
No.  166. 

t  G.  C.  Whipple  and  M.  C.  Whipple,  Am.  J.  Pub.  Health,  1913,  3,  p.  1140. 

9 


lO  AIR,   WATER,   AND    FOOD 

ber  gradually  decreasing  as  the  height  above  the  street  increased, 
until  only  about  27,000  were  found  in  the  air  taken  from  the 
fifty-seventh  floor  of  the  Wool  worth  Building,  716  feet  high.  In 
a  house,  school  room  or  public  building  the  numbers  of  dust 
particles  are  equally  variable,  wuth  a  tendency  to  be  somewhat 
higher,  depending  on  the  location  of  the  building,  and  whether 
or  not  the  air  entering  is  purified.  Thus  in  an  investigation  of 
the  air  of  school  rooms,*  few  cases  were  found  where  the  num- 
bers were  less  than  200,000  per  cubic  foot,  and  they  varied  from 
this  to  over  1,500,000,  the  greater  proportion  being  between 
200,000  and  600,000,  much  higher  than  is  generally  found  in 
outdoor  air.  The  numbers  of  bacteria  found  in  the  air  are  small 
compared  to  the  dust  particles,  there  being  about  200"  ^^  many 
in  outdoor  air,  and  even  less  in  indoor  air,  in  85  per  cent  of  the 
samples  taken  in  school  rooms  f  the  number  of  micro-organisms 
being  less  than  150  per  cubic  foot.  In  country  districts  the 
numbers  of  both  dust  particles  and  bacteria  in  the  air  are  ex- 
tremely small. 

Under  ordinary  conditions  the  presence  of  dust  and  bacteria 
has  no  particular  significance.  In  fact  it  is  the  opinion  of  most 
sanitarians  that  the  danger  of  the  spread  of  disease  by  the 
carrying  of  bacteria  through  the  air  is  small,  the  contact  neces- 
sary for  this  to  happen  being  much  closer  than  generally  exists 
in  oflices  and  schoolrooms.  There  are  certain  special  cases 
where  dust  particles  may  be  harmful,  —  such  as  the  dust  con- 
sisting of  small  particles  of  metal  found  in  certain  factories, 
and  the  organic  dust  found  in  the  air  in  certain  rooms  in  textile 
mills.  Some  of  these  dusts,  such  as  white  lead,  are  themselves 
actually  poisonous  to  the  system,  while  others  lodge  in  the 
lungs  and  lower  the  vitahty  so  that  pneumonia  and  tuberculosis 
are  more  liable  to  gain  a  footing. 

Poisonous  gases  are  occasionally  found  in  air,  —  the  most 
important  being  carbon  monoxide  which  comes  from  leaky  gas 
jets  or  pipes,  or  from  a  defective  furnace.     As  this  gas  has  al- 

*  Winslow,  Am.  J.  Pub.  Heallh,  1913,  3,  p.  1158. 
t  Winslow,  loc.  cil. 


AIR   AND   HEALTH  II 

most  no  odor,  insensibility  may  occur  without  the  victim  realiz- 
ing what  is  taking  place.  For  this  reason  it  has  been  found 
necessary,  where  this  gas  is  used  for  lighting,  to  require  the  in- 
troduction into  it  of  some  substances  with  strong  odors.  Car- 
bon monoxide  acts  as  a  poison  by  combining  with  the  hsemo- 
globin  of  the  blood,  and  preventing  the  absorption  of  oxygen. 

In  the  air  of  mines,  methane,  —  or  fire  damp  as  it  is  called,  — 
is  sometimes  present.  This  forms  an  explosive  mixture  with 
oxygen,  and  is  frequently  the  cause  of  mine  explosions. 

Respiration.  —  External  respiration  consists  of  alternately 
filling  and  emptying  the  lungs.  In  the  lungs,  oxygen,  breathed 
in  with  the  air,  is  exchanged  for  carbon  dioxide  brought  to  the 
lungs  by  the  blood.  The  blood  leaving  the  lungs  contains  oxy- 
gen which  is  carried  to  all  parts  of  the  body,  and  passes  *  from 
the  blood  in  the  capillaries  into  the  tissues  where  oxidation  takes 
place.  The  carbon  dioxide  formed  passes  back  into  the  blood 
and  hence  into  the  lungs.  Expired  air,  therefore,  contains  less 
oxygen  and  more  carbon  dioxide  than  inspired  air.  An  average 
composition  would  be,  —  oxygen,  16.03  P^r  cent;  carbon  di- 
oxide, 4.38  per  cent;  nitrogen,  etc.,  79  per  cent. 

The  process  of  exchange  of  oxygen  and  carbon  dioxide  in  the 
lungs  is  partly  a  physical  one,  —  that  is,  the  vapor  pressure  of 
oxygen  is  greater  in  the  lungs  than  in  the  blood,  and,  therefore, 
oxygen  passes  from  the  former  to  the  latter.  With  carbon 
dioxide  the  reverse  is  true.  Therefore,  if  air  high  in  carbon 
dioxide  is  breathed  into  the  lungs  this  will  increase  the  vapor- 
pressure  of  this  substance,  and  hinder  the  elimination  of  it  from 
the  blood.  But  it  appears  to  be  impossible  to  account  for  the 
interchange  of  gases  on  a  purely  physical  basis,  and,  therefore, 
it  is  thought  that  enzymes,  which  aid  in  the  interchange,  are  at 
work. 

Comfort.  —  The   first   two   theories   that   were   advanced    to 

account  for  effects  of  discomfort  when  a  room  becomes  "close" 

were  based  on  the  supposition  that  the  products  of  respiration 

were  poisonous  when  taken  back  into  the  lungs.     In  one  theory 

*  See  Haramarsten-Mandel.     "A  Text-book  of  Physiological  Cheinistr>-." 


12  AIR,   WATER,   AND   FOOD 

this  poisonous  substance  was  supposed  to  be  carbon  dioxide. 
That  animals  cannot  live  in  an  atmosphere  composed  of  nitro- 
gen and  carbon  dioxide,  and  that  oxygen  is  necessary  has  long 
been  known,  but  it  was  thought  that  carbon  dioxide  had  a 
specific  poisonous  action  and,  therefore,  should  be  present  in  any 
air  used  for  human  beings,  in  only  very  small  amounts.  This 
theory  has  been  entirely  disproved  and  carbon  dioxide  can  no 
longer  be  regarded  as  in  itself  poisonous.  If  too  much  of  the 
oxygen  in  the  air  becomes  displaced  by  carbon  dioxide  it  is  im- 
possible for  animals  to  utilize  the  oxygen  left,  but  this  only 
happens  when  the  oxygen  content  decreases  to  about  12  per 
cent.  Practically  such  a  low  per  cent  is  never  found,  as  inter- 
change of  the  air  between  a  room  and  the  outside  is  continually 
going  on  around  windows  and  through  walls.  If,  however,  the 
•oxygen  is  allowed  to  remain  at  about  21  per  cent,  very  large 
quantities  of  carbon  dioxide  may  be  present  without  any  ill 
effects.  Experiments  have  shown  conclusively  *  that  carbon 
dioxide  cannot  be  blamed  for  discomfort  in  a  crowded  hall  or 
theatre. 

The  other  theory, — known  as  the  "crowd  poison"  theory 
was  based  on  some  experiments  which  seemed  to  show  that 
organic  poisons  were  given  off  during  respiration,  and  that  these 
substances  were  the  cause  of  the  headaches  and  nausea  some- 
times experienced  by  sensitive  persons  in  "close"  rooms.  At 
the  present  time  there  are  some  adherents  to  this  theory,  but 
there  has  been  little  real  evidence  produced  in  its  support.  The 
first  proofs  of  the  non-poisonous  character  of  exhalations  were 
obtained  by  Formanek  in  a  long  series  of  experiments  f  and 
more  recently  Winslow  J  using  the  principles  of  anaphylaxis 
failed  to  obtain  any  results  which  showed  the  presence  of  the 
poisons  (or  toxins)  in  expired  air. 

At  the  present  time  it  is  quite  generally  believed  that  sen- 

*  See  Crowder.  "Ventilation  of  Sleeping  Cars."     Arch.  Intern.  Med.,  1911,  7, 

PP-  85-133- 

t  Archiv  fiir  Hygiene,  1900,  38,  p.  i. 
I  Loc.  cit. 


AIR   AND    HEALTH 


13 


sations  of  comfort  and  discomfort  are  dependent  upon  the  rate 
of  loss  of  heat  from  the  body.  If  this  is  normal,  then  comfort 
results,  if  either  too  high  or  too  low,  then  discomfort,  headaches 
and  nausea  may  follow.  Just  what  this  heat  loss  should  be, 
measured  in  any  system  of  units,  is  not  known,  but  certain  of 
the  methods  by  which  the  loss  takes  place,  and  the  factors 
which  influence  the  rate  may  be  discussed. 

There  are  three  ways  by  which  heat  can  be  transferred  from 
the  body  to  the  surrounding  atmosphere,  (i)  Evaporation.  — 
The  change  from  the  liquid  to  the  gaseous  state  is  accompanied 
by  an  absorption  of  heat.  Thus  when  water  evaporates  from 
the  surface  of  the  body,  heat  is  removed  with  it.  (2)  Trans- 
mission (by  conduction  and  convection).  Heat  passes  from  a 
warm  to  a  cold  body  when  the  two  are  in  contact.  For  the 
greater  part  of  the  year  the  animal  body  is  warmer  than  the 
atmosphere,  and,  therefore,  the  latter  is  continually  receiving 
heat  from  the  body.  Since  warm  air  rises,  convection  currents 
may  be  set  up  carrying  away  the  heat  already  given  up  to  the 
air.  (3)  Radiation.  —  The  first  two  methods  depend  directly 
on  the  presence  of  matter.  In  radiation  heat  is  transferred  in 
all  directions  by  means  of  ether  waves,  and  the  medium  through 
which  the  radiation  takes  place  does  not  necessarily  become 
heated.  There  is  no  data  available  on  the  loss  of  heat  from  the 
body  in  this  way,  and  we  do  not  know  what  part  it  actually 
plays  in  comfort. 

These  three  methods  by  which  heat  may  be  given  off  from 
the  body  may  be  acting  simultaneously,  —  in  fact  they  generally 
are  doing  so,  —  and  one  or  more  may  be  negative  in  its  action,  — 
that  is  may  be  supplying  heat  to  the  body.  Further,  while  they 
act  entirely  independently  of  each  other,  they  are  each  in- 
fluenced by  the  same  conditions  of  the  atmosphere,  and  it  is 
these  physical  conditions  which  are  the  ones  capable  of  regu- 
lation, and  which  determine  good  or  bad  ventilation.  These 
are,  —  temperature,  humidit}'  and  motion. 

Temperature.  —  Temperature  affects  evaporation,  because  the 
higher  the  temperature  of  the  air  the  more  moisture  is  it  cajxible 


14  AIR,   WATER,   AND    FOOD 

of  taking  up.  It  affects  conduction,  because  the  greater 
the  difiference  of  temperature  between  two  bodies  the  greater  the 
amount  of  heat  passing  from  that  at  the  higher  to  that  at  the 
lower  temperature.  It  affects  convection,  because  convection 
currents  are  started  by  warm  air  rising  and  cooler  air  taking  its 
place. 

Humidity.  —  Heat  loss  by  evaporation  is  more  dependent  on 
humidity  than  on  any  other  factor.  Relative  humidity  is  a 
measure  of  the  per  cent  saturation  of  the  air  by  water  vapor, 
and  it  is  obvious  that  the  higher  the  humidity  the  less  will  be 
the  opportunity  for  the  air  to  take  up  more  moisture,  and, 
therefore,  the  less  rapid  the  evaporation  from  the  body.  Trans- 
mission of  heat  from  the  body  is  affected  by  the  humidity,  be- 
cause moist  air  is  a  better  conductor  than  dry  air,  and,  therefore, 
the  higher  the  humidity  the  greater  the  rate  of  heat  conduction. 
(Relative  humidity,  as  can  be  seen  from  a  foregoing  discussion, 
is  itself  affected  by  the  temperature.) 

Motion.  —  The  motion  of  the  air  influences  evaporation  by 
carrying  away  from  the  body  more  or  less  rapidly  the  air  which 
has  become  completely  saturated  with  moisture,  and  thus  al- 
lowing access  to  unsaturated  air.  If  the  air  and  the  body  are 
perfectly  quiet  evaporation  will  be  gradually  retarded  until  it 
is  nearly  zero.  Convection  currents  are  movements  in  the  air 
started  by  differences  in  temperature.  These  movements  will 
be  greatly  increased  by  any  motion  in  the  air,  and,  therefore, 
the  greater  the  motion  the  more  rapid  will  be  the  transference 
of  heat  in  this  way. 

It  is  important  to  remember  that  these  three  factors,  tem- 
perature, humidity  and  motion,  —  are  always  acting  simul- 
taneously, and  that  there  may  be  an  increase  in  the  rate  of  heat 
loss  above  the  normal  by  one  or  more  of  them  at  the  same  time 
that  the  rest  tend  to  decrease  this  rate.  Furthermore,  the  same 
factor,  humidity  for  example,  may  tend  to  increase  the  heat  loss 
above  the  normal  by  one  method,  —  perhaps  by  evaporation,  — 
while  at  the  same  time,  the  same  degree  of  humidity  may  tend 
to  decrease  below  the  normal  the  heat  loss  by  another  method, 


AIR  AND   HEALTH  1 5 

perhaps  by  transmission.  The  degree  of  comfort  felt  under  any 
specified  conditions  is,  therefore,  the  resultant  of  all  effects,  some 
tending  to  increase  and  others  to  decrease  the  rate  of  heat  loss 
from  the  normal. 

This  can  be  readily  illustrated.  Suppose  that  the  temper- 
ature is  95°  F.,  the  humidity  90  per  cent  and  there  is  but  very 
little  motion  in  the  air.  The  result  is  well  known,  —  a  feeling 
of  heaviness  and  considerable  discomfort.     Why? 

(i)  The  high  temperature  allows  the  air  to  take  up  a  con- 
siderable amount  of  moisture,  thus  tending  to  increase  the  heat 
loss  by  evaporation,  with  the  consequent  cooling  effect  on  the 
body.  On  the  other  hand,  the  heat  loss  by  conduction,  con- 
vection and  radiation  arc  only  very  small  as  they  depend  on 
the  difference  of  temperature  of  the  body  and  the  air. 

(2)  The  high  humidity  prevents  the  rapid  evaporation  of 
moisture,  and,  therefore,  tends  to  decrease  the  heat  loss  from  the 
body.  This  more  than  counteracts  the  increased  capacity  of 
the  air  for  moisture,  due  to  the  high  temperature.  On  the 
other  hand,  the  high  humidity  makes  the  air  a  better  conductor 
of  heat,  and,  therefore,  tends  to  increase  the  heat  loss  by  con- 
duction. This,  again,  is  counteracted  by  the  high  temperature, 
temperature  being  the  more  important  factor  in  this  method  of 
loss. 

(3)  The  very  slight  motion  of  the  air  tends  to  decrease  the 
heat  loss  by  evaporation  and  convection. 

The  net  result  is  that  heat  does  not  leave  the  body  as  rapidly 
as  it  should,  and  we  feel  hot  and  uncomfortable. 

Application  of  this  theory  of  regulation  of  loss  of  heat  is  not 
wholly  adequate  to  explain  all  conditions.  Another  factor  seems 
to  be  involved,  that  of  loss  of  moisture,  apart  from  any  loss  of 
heat  which  accompanies  this.  "Probably  much  of  the  harm 
attributed  to  damp  and  to  cold  is  due  to  diminished  water  cir- 
culation, etc."*  With  this  added  factor  it  is  possible  to  ex- 
plain most  of  the  uncomfortable  conditions.  The  uncertainty 
of  the  theory  lies  in  the  fact  that  we  have  been  unable  to  test  it 

*  Macfie,  Air  and  Health. 


i6 


AIR,  WATER,  AND  FOOD 


THE  CURVE  OF  COMFORT 


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Mean  annual  temperature  and  humidity  of  health  resorts: 


1  Algiers  5 

2  Alexandria  6 

3  Cairo  7 

4  Bermuda  8 

Unfavorable  to  white  man's  residence: 

9  New  Orleans  12 

10  ,  Havana  13 


Arequipa 
Luxor-winter 
Los  Angeles 
Madeira 


Persia 
India 


II      Malay  Archipelago         14      Singapore 
A-B    Most  comfortable  for  indoor  workers  (Hill). 


AIR   AND   HEALTH  17 

experimentally  and  to  determine  the  exact  heat  loss  due  to  each 
factor. 

Hill  *  has  plotted  a  series  of  curves  which  are  intended  to 
represent  the  various  conditions  of  comfort  in  terms  of  tem- 
perature and  humidity.  Thus  it  is  seen  that  a  temperature  of 
55°  F.  and  a  humidity  of  70  per  cent  gives  comfort,  and  as  the 
temperature  increases  the  humidity  must  be  decreased.  At 
68°  F.,  the  temperature  generally  desired  in  the  house,  the 
humidity  must  be  around  50  per  cent. 

Ventilation.  —  In  ventilating  a  public  building  or  a  house,  it 
is  necessary  to  supply  a  sufficient  quantity  of  air  in  the  proper 
condition.  In  most  cases  this  condition  is,  that  the  air  in  the 
room  shall  be  at  a  temperature  of  68°  to  70°  F.,  and  with  a 
humidity  of  50  to  70  per  cent.  As  long  as  the  humidity  does 
not  go  too  high,  it  seems  to  be  a  secondary  factor  so  far  as  health 
is  concerned.  More  discomfort  is  felt  from  overheating  than 
from  any  other  cause.  This  is  also  true  in  many  factories,  but 
there  are  some  where  high  humidity  must  be  considered,  such 
as  is  necessary  to  maintain  in  connection  with  certain  textile 
operations.  It  should  be  remembered  that  the  higher  the  tem- 
perature the  more  sensitive  does  one  become  to  high  himiidity. 

Another  condition  which  must  be  met  in  ventilation  practice 
is  that  governed  by  the  carbon  dioxide  content  of  the  air.  As 
pointed  out  above,  this  substance  is  not  itself  poisonous,  but  it 
is  useful  in  serving  as  an  index  of  the  amount  of  unused  air  be- 
ing supplied.  The  normal  individual  gives  off  from  0.6  to  0.8 
cubic  feet  of  carbon  dioxide  per  hour,  and  this  will  gradually 
accumulate  in  a  room  unless  the  air  is  continually  being  replaced. 
The  amount  of  carbon  dioxide  present  in  a  room  can,  therefore, 
be  used  to  determine  whether  or  not  there  is  sufficient  replace- 
ment of  used  air  by  fresh  air.  The  allowable  amount  of  carbon 
dioxide  is  about  10  parts  per  10,000  of  air.  Arnounts  above  this 
may  be  allowed  in  certain  special  cases  where  the  carbon  dioxide 
does  not  come  from  man  or  animals.  If  only  6  or  7  parts  are 
present,  the  ventilation  may  be  considered  excellent.     In  order 

*  Hill,  Recent  Advances  in  Physiology  and  Biochemistrj'. 


l8  AIR,   WATER,    AND    FOOD 

to  accomplish  this  about  2000  cubic  feet  of  fresh  air  per  person 
per  hour  must  be  supplied.  The  amounts  actually  recommended 
depend  somewhat  on  the  use  to  which  the  room  or  building  is 
to  be  put,  these  amounts  varying  between  1000  cu.  ft.  for  a 
waiting  room  and  2500  for  a  hospital.  Where  it  is  difficult  to 
determine  how  many  people  will  be  present  the  calculations  may 
be  based  on  the  number  of  complete  changes  of  air  per  hoar, 
these  being  from  one  to  five  in  a  residence,  and  from  one  to  two 
in  an  auditorium.* 

It  is  also  possible  to  calculate  from  analytical  data  the  inter- 
change of  air  going  on  under  given  conditions,  and  thus  test  the 
efficiency  of  a  ventilating  system.  If,  after  a  room  has  been 
occupied  and  the  occupants  removed,  the  air  is  analyzed  for 
carbon  dioxide,  the  room  allowed  to  remain  a  definite  length  of 
time,  and  another  analysis  made,  the  interchange  may  be  cal- 
culated from  a  formula  given  by  Barker:  f 


^=f'°^(l^:) 


where  C  is  the  contents  of  the  room  in  cubic  feet,  T  the  time  in 
hours  between  the  original  amount  of  carbon  dioxide  ki  in  one 
cubic  foot  of  air,  and  the  final  amount  ^2  in  one  cubic  foot  of 
air,  a  the  proportion  of  carbon  dioxide  in  one  cubic  foot  of  pure 
atmospheric  air,  and  V  the  interchange  in  cubic  feet  per  hour. 

Ventilation  depends  on  the  movement  of  air  currents  in  such 
a  way  as  to  continually  supply  fresh  air  and  to  remove  used 
air.  This  must  be  done  so  that  no  drafts  will  be  felt  at  any 
part  of  the  room.  The  system  actually  used  will  depend  on 
the  kind  of  building  and  room,  —  as  well  as  on  the  kind  of  heat- 
ing used.  In  the  ordinary  dwelling  house  ventilation  is  almost 
ahvays  left  to  look  after  itself.  Even  in  the  best  built  houses 
there  is  going  on  constantly  an  interchange  of  air  around  the 
windows  and  doors.     This  is  not  sufficient  on  winter  evenings 

*  Greene,  "Elements  of  Heating  and  Ventilation,"  p.  23. 

t  Baker,  "The  Theory  and  Practice  of  Heating  and  Ventilation,"  p.  164.  A 
number  of  other  useful  ventilating  formula;  are  also  given. 


AIR   AND   HEALTH  19 

when  kerosene  or  gas  lamps  are  burning,  and  most  rooms  soon 
become  stuffy.  To  aid  this  natural  ventilation,  windows,  open 
fire  places  and  hot  air  furnaces  are  used.  Excellent  results  may 
be  obtained  from  the  careful  use  of  the  open  window,  but  it  re- 
quires considerable  time  as  well  as  care  to  operate  them  so  that 
no  drafts  will  result.  Where  a  hot  air  system  of  heating  is  used 
a  house  may  be  well  ventilated,  —  the  air  which  is  forced  in 
through  registers  going  out  after  proper  circulation,  through  ven- 
tilators or  around  windows.  Care  should  be  taken  to  place 
registers  to  get  this  circulation. 

In  a  large  building,  —  office,  educational,  or  auditorium,  —  the 
problem  is  somewhat  different.  Here  it  is  useless  to  depend  on 
natural  ventilation  and  some  artificial  means  must  be  employed. 
There  are  two  general  methods  of  air  circulation  in  use,  upward 
and  downward.  Both  have  their  advantages  and  disadvantages. 
Upward  ventilation  would  seem  theoretically  the  best,  as  ex- 
pired air,  being  warm,  rises  and  creates  an  upward  current, 
which  can  be  easily  drawn  into  an  outlet.  This  system  can  be 
used,  but  it  presents  certain  difficulties.  The  first  is  that  un- 
less air  comes  into  the  room  through  a  very  large  number  of 
small  holes  in  the  floor,  drafts  of  cold  air  around  the  feet  are 
certain  to  be  felt.  This  would  only  be  practical  in  an  audi- 
torium with  stationary  seats.  Besides,  objection  is  sometimes 
made  that  odors  from  the  clothing  are  made  more  noticeable  by 
being  carried  past  the  nose.  The  reverse  system,  downward  ven- 
tilation, seems  to  be  more  practical.  Here  the  air  is  introduced 
from  the  ceiling  and  is  drawn  out  through  ducts  in  or  near  the 
floor.  More  often  air  is  introduced  from  the  walls  of  the  room. 
In  this  case  it  is  necessary  to  so  arrange  the  inlet  and  outlet 
that  air  from  the  former  will  circulate  around  the  room  before 
reaching  the  latter.  To  do  this,  the  outlet  is  generally  placed 
a  little  below  the  inlet  on  the  same  wall,  this  being  on  the  cold 
side  of  the  room.  The  air  may  be  forced  into  the  room  under 
pressure  from  a  fan,  called  the  plenum  system,  or  may  be  drawn 
out  from  the  room  by  a  fan  in  the  outlet,  called  the  vacuum 
system. 


20  AIR,    WATER,   AND    FOOD 

In  cities  where  there  is  necessarily  much  smoke  and  dirt, 
it  may  be  considered  best  to  purify,  in  some  way,  the  air 
entering  a  building.  The  simplest  method  is  to  screen  the  in- 
coming air  through  fine  wire  gauze  or  cheese  cloth.  A  more 
effective  way  is  by  means  of  air  washers.  All  of  these,  and 
there  are  a  number  of  them  on  the  market,  depend  on  the  pas- 
sage of  the  air  through  a  spray  of  water  which  removes  dirt, 
bacteria  and  soluble  substances.  Since  these  machines  spray 
water  into  the  air  they  are  also  humidifiers,  and  may  be  used  as 
such,  particularly  in  textile  factories  where  it  is  necessary  to 
carry  on  certain  operations  in  moist  air. 

It  is  also  possible  to  take  air  out  of  a  room,  wash  it,  cool  it 
and  send  it  back  into  the  same  room.*  This  would  effect  a 
saving  of  coal  if  it  w^ere  practical  to  operate. 

Another  method  which  has  been  in  some  use  for  purifying  air 
is  by  means  of  ozone.  During  the  last  year  there  has  been  much 
discussion  on  this  subject,  f  and  very  serious  doubts  have  been 
thrown  on  the  real  usefulness  of  this  method.  That  ozone  in 
the  presence  of  a  large  amount  of  moisture  is  a  good  disinfectant 
cannot  be  denied,  but  under  the  dry  conditions  of  the  atmos- 
phere its  germicidal  efi'ect  is  small.  However,  in  most  cases  it 
is  not  bacteria  which  we  need  to  kill,  but  odors.  On  this  point 
the  evidence  is  not  quite  so  clear.  Most  are  agreed  that  the 
odors  disappear,  but  it  is  still  a  question  whether  the  substances 
producing  them  are  actually  destroyed,  or  whether  the  odors 
are  masked  by  those  of  ozone.  From  a  standpoint  of  health, 
this  would  also  be  immaterial  if  it  could  be  proved  that  the 
ozone  itself  was  harmless  to  breathe.  At  the  present  time  the 
evidence  seems  to  be  the  other  way. 

*  See  article  on  Recirculated  Air.     McCurdy,  Am.  Phys.  Ed.  Rev.,  Dec,  1913. 
t  Jordan  and  Carlson,  J.  Am.  Med.  Assn.,  1913,  61,  pp.  1007-1012;    Norton, 
Eng.  Rec,  1913,  68,  p.  732;   Vosmaer,  /.  Ind.  E)ig.  Chcm.,  1914,  6,  p.  229. 


CHAPTER   III 
air:  analytical  methods 

In  an  investigation  of  the  air  of  any  room  or  public  building 
it  is  not  enough  to  make  one  or  two  observations,  as  these  might 
be  entirely  misleading,  but  a  sufficient  number  must  be  taken 
to  get  a  fair  estimate  of  the  conditions.  Thus  in  a  room,  read- 
ings of  the  physical  instruments  must  be  made  and  samples 
for  chemical  analysis  taken  at  a  number  of  points,  and  these 
repeated  at  intervals  of  five  or  lo  minutes  until  six  or  eight  have 
been  taken.  Slight  changes  constantly  occur  which  are  not  of 
any  importance  in  practical  work,  but  fortunately  most  of  the 
instruments  and  most  of  the  methods  used  are  not  delicate 
enough  to  be  influenced  by  changes  of  this  character.  In  short, 
it  is  average  conditions  which  are  of  importance,  and  which 
should  be  recorded. 

Physical  Determinations.  —  Temperature.  —  The  use  of  the 
thermometer  is  too  well  known  to  need  any  detailed  statement. 
Mercurial  thermometers  are  the  most  accurate  for  practical 
work,  but  care  should  be  taken  that  the  bulb  of  the  thermome- 
ter is  suspended  in  the  air  and  not  placed  against  a  wooden 
back,  as  in  the  latter  case  the  reading  lags  behind  the  actual 
changes  in  the  temperature  of  the  air.  Where  it  is  desired  to 
have  a  continuous  record,  recording  thermometers  are  to  be 
recommended.  These  depend  on  the  contraction  and  expan- 
sion of  a  metal  combination,  with  the  changes  of  temperature, 
the  metal  being  connected  with  a  pen  which  records  the  changes 
on  a  paper  disc  moved  by  clockwork. 

Pressure.  —  Air  pressure  is  measured  by  barometers,  of  which 
there  are  two  types,  —  mercurial  and  anaeroid,  both  of  which 
are  well  known.  Since  the  barometric  reading  depends  on  the 
weight  of  the  column  of  air  above  the  instrument,  the  reading 


22  AIR,   WATER,    AND    FOOD 

will  vary  with  the  distance  above  sea  level,  and  with  the  com- 
position of  the  air.  In  the  latter  case  the  only  important  factor 
is  moisture.  As  water  vapor  is  lighter  than  dry  air,  the  larger 
the  moisture  content  the  lighter  the  moist  air  and  the  less  the 
pressure.  Thus  a  low  barometric  reading  indicates  the  ap- 
proach of  a  storm. 

Humidity.  —  Relative  humidity  has  already  been  described. 
The  most  accurate  method  of  measurement  is  by  means  of  wet 
and  dry  bulb  thermometers.  The  rate  of  evaporation  of  water 
into  air  at  any  one  temperature  depends  on  the  amount  of 
moisture  already  present.  Since  evaporation  is  accompanied  by 
absorption  of  heat,  the  surface  from  which  the  water  evaporates 
will  be  cooled  in  proportion  to  the  rate  of  evaporation.  If  the 
bulb  of  a  thermometer  is  surrounded  by  a  film  of  moisture, 
which  can  readily  be  done  by  means  of  a  piece  of  cloth  or  wick 
with  one  end  dipped  in  a  reservoir  of  water,  this  cooling  can  be 
measured  by  the  lowering  of  the  temperature  below  that  of  a 
thermometer  whose  bulb  is  surrounded  by  air  alone,  and  the 
lowering  is  proportional  to  the  relative  humidity.  In  the  ap- 
pendix will  be  found  a  table  from  which  the  relative  humidity 
can  be  obtained  from  the  reading  of  the  dry  and  wet  bulb  ther- 
mometers. In  order  that  the  wet  bulb  thermometer  may  come 
quickly  to  equilibrium  an  instrument  called  the  psychrometer 
has  been  devised  for  rapidly  rotating  the  thermometers. 

Another  method  of  measuring  the  humidity  is  by  means  of 
the  hair  hygrometer.  In  this  instrument  a  number  of  horse 
hairs  arc  placed  under  tension  by  means  of  a  small  weight. 
The  distance  to  which  the  hairs  will  be  stretched  will  depend  on 
the  amount  of  moisture  taken  up  from  the  air,  —  the  higher 
the  moisture  the  greater  the  stretching.  The  weight  can  be 
readily  connected  to  an  indicator  which  will  record  the  rela- 
tive humidity  on  a  dial,  or  a  pen  can  be  attached,  to  make  a 
recording  instrument,  in  a  similar  manner  to  that  used  with  a 
recording  thermometer. 

Motion.  —  Where  the  velocity  of  air  is  considerable,  as  in  the 
case  of  wind  or  in  such  places  as  ventilation  ducts,  measure- 


AIR:   ANALYTICAL   METHODS 


23 


merits  can  be  made  by  the  use  of  anemometers.  However,  in  a 
room,  the  movement  of  air  is  much  too  slow,  and  the  direction 
of  currents  too  varied,  for  such  an  instrument  to  be  of  use. 
The  best  method  is  by  use  of  smoke  from  a  joss  stick  or  cigar.* 

Dust.  —  The  simplest  method  for  determining  dust  in  air  is  to 
draw  a  measured  quantity  of  air  through  a  weighed  tube  con- 
taining a  cotton  plug.  For  this  it  is  necessary  to  have  a  suction 
pump,  —  the  variety  which  may  be  attached  to  a  water  faucet 
is  useful,  —  a  meter,  such  as  a  gas  meter,  and  a  tube  containing 
a  cotton  plug.  The  tube  with  the  plug  should  be  dried  in  a 
desiccator  before  each  weighing  as  moisture  may  be  absorbed 
from  the  air  passed  through.  Knowing  the  amount  of  air  and 
the  increase  of  weight  of  the  cotton  filter,  the  amount  of  dust 
per  unit  volume  of  air  can  be  calculated.  Where  the  amount  of 
dust  is  large,  the  cotton  plug  can  be  replaced  by  one  of  granulated 
sugar.  The  amount  of  dust  is  then  determined  by  dissolving 
the  sugar  in  water  and  then  filtering  through  a  weighed  Gooch 
crucible. 

The  most  accurate  determinations  of  dust  particles  can  be 
made  by  m^eans  of  the  "Dust  Counter"  or  the  "Koniscope." 
Both  of  these  instruments  f  are  too  expensive  to  be  very  generally 
used. 

An  apparatus  for  taking  dust  samples  of  air  has  recently  been 
described  by  Baskerville,|  and  would  seem  to  be  useful  and 
sufficiently  accurate  for  practical  purposes. 

Chemical  Determinations.  —  The  first  systematic  study  of 
the  atmosphere  was  made  by  Scheele,  in  1779,  shortly  after  the 
discovery  of  oxygen.  Since  that  time  more  and  more  accurate 
methods  have  gradually  been  developed,  culminating  in  that 
used  recently  by  Benedict.  § 

*  Shaw,  "  Air  Currents  and  the  Laws  of  Ventihition."     Cambridge.  1907. 

t  See  "Standard  Methods  for  the  Bacterial  Examination  of  Air,"  Am.  Pub. 
Health  Assn.,  1910,  p.  38. 

X  J.  hid.  Eng.  Cliem.,  1914,  6,  p.  238. 

§  For  a  detailed  history  of  air  analysis  see  Benedict,  "The  Composition  of  the 
Atmosphere  with  Special  Reference  to  its  Oxygen  Content,"  Carnegie  Institution 
of  Washington,  191 2,  Publication  No.  166. 


24  AIR.   WATER,   AND    FOOD 

In  practice  the  only  chemical  test  made  on  air  is  that  for 
carbon  dioxide.  In  cases  of  poisoning,  tests  may  be  made  for 
carbon  monoxide  or  methane,  and  in  experiments  with  respira- 
tion, oxygen  determinations  together  with  those  for  carbon 
dioxide  are  considered  necessary. 

The  methods  for  the  determination  of  carbon  dioxide  are  all 
based  on  absorption  by  alkalies,  the  amount  of  this  absorption 
being  measured  either  by  direct  determination  of  the  diminution 
of  a  given  volume  of  air,  or  by  determination  of  the  amount  of 
alkali  used  for  the  absorption. 

Collection  of  Samples.  — ■  Methods  for  collecting  samples  of  air 
for  chemical  analysis  will  vary  somewhat  with  the  method  and 
apparatus  used.  In  certain  cases  the  sample  is  measured 
directly  into  the  analytical  apparatus,  while  in  others,  —  and 
these  are  the  more  practical  methods,  — •  the  sample  is  first  col- 
lected in  a  balloon  or  bottle.  Where  large  amounts  are  needed, 
as  in  the  Pettenkofer  method,  the  samples  are  collected  in  a 
four-  or  six-liter  bottle,  the  volume  of  which  has  been  determined 
by  weighing  both  empty  and  filled  with  water.  The  bottle  is 
fitted  with  a  two-hole  rubber  stopper  with  a  short  piece  of  glass 
tubing  to  serve  as  an  inlet  in  one  hole  and  a  long  brass  tube  ex- 
tending to  the  bottom  of  the  bottle,  in  the  other  hole.  This 
brass  tube  is  connected  to  a  bellows  with  the  valves  arranged  so 
that  air  will  be  drawn  out  of  the  bottle.  Pumping  should  be 
continued  until  the  air  originally  in  the  bottle  has  been  entirely 
replaced,  which  will  take  from  30  to  50  strokes  of  the  bellows. 
The  stopper  and  tube  are  then  removed,  and  the  bottle  closed 
with  a  stopper  as  described  on  page  34. 

For  the  Walker  and  the  Cohen  and  Appleyard  methods  a 
much  smaller  volume  is  all  that  is  needed,  —  from  500  c.c.  to 
two  liters.  The  simplest  method  is  to  fill  the  bottle  with  water 
and  pour  it  out.  This  has  the  disadvantage  that  expired  air 
from  the  collector  may  reach  the  bottle. 

A  better  method  is  to  fit  two  bottles  each  with  a  2-hole 
rubber  stopper.  In  one  hole  of  the  stopper  of  bottle  (A)  (Fig.  i) 
insert  a  short  piece  of  glass  tubing,  and  in  the  other  a  longer 


AIR:  ANALYTICAL   METHODS 


25 


piece  of  tubing  extending  nearly  to  the  bottom  of  the  bottle. 
In  the  stopper  of  {B)  insert  a  short  piece  of  glass  tubing  just 
reaching  through  the  stopper,  and  a  longer  tube  extending 
nearly  to  the  bottom,  and 
fitted  with  a  piece  of  small 
bore  rubber  tubing  and  a 
pinch  clamp.  Connect  the 
short  tube  of  bottle  {B)  with 
the  long  tube  of  (^4)  by  means 
of  a  rubber  tube  and  close 
with  a  pinch  clamp.  Fill  {B) 
with  recently  boiled  water, 
open  clamp  (a),  close  clamp 
{h)  and  insert  stopper  with 
connections,  into  the  bottle. 
Then  close  {a).  Invert  {B) 
at  the  point  at  which  the  sam- 
ple is  to  be  taken.  Release 
the  pinch  clamp  (a),  and  then 
open  the  clamp  {b).  The  bot-  . 
tie  filled  with  air  (B)  is  then 
closed  with  a  solid  rubber 
stopper  and  is  ready  for 
analysis.  If  bottle  {A)  is 
larger  than  {B)  it  can  be 
used,  together  with  the  water,  for  taking  a  number  of  samples 
of  air. 

Another  method  by  which  sampling  is  made  easier,  but  which 
does  not  give  such  accurate  results,  is  the  steam  vacuum  method. 
The  apparatus  is  set  up  as  in  Fig.  2.  Steam  is  supplied  from  a 
two-quart  oil  can  nearly  filled  with  water,  or  if  preferred,  from  a 
liter  flask.  A  rubber  tube  and  piece  of  glass  tubing  connects 
the  steam  can  with  the  inverted  bottle,  the  size  of  which  de- 
pends on  the  method  of  analysis  used,  the  tube  extending  to 
within  an  inch  of  the  bottom  of  the  bottle.  The  bottles  are 
made  for  ground  glass  stoppers,   but  are  fitted  with   rubber 


Fig.  I. 


26 


AIR,   WATER,   AND   FOOD 


stoppers  to  which  have  been  applied  a  thin  coating  of  vaseline. 
Too  much  vaseline  should  be  avoided,  as  it  prevents  the  stopper 
staying  in  after  the  sample  has  been  collected.  The  rubber 
stoppers  should  be  one  size  larger  than  would  ordinarily  be  used. 
To  prepare  the  bottle,  fill  the  can  two-thirds  full  with  water, 
and  boil  for  a  few  minutes  to  expel  carbon  dioxide  and  air.     In- 


FlG.   2. 

vert  the  empty  bottle  over  the  end  of  the  tube,  and  allow  to 
remain  for  three  minutes.  Keeping  the  bottle  inverted,  re- 
move it  from  the  tube,  and  quickly  insert  the  rubber  stopper. 
The  stopper  may  be  pushed  in  more  securely  by  holding  it 
against  the  table  with  a  slight  pressure,  and  keeping  it  there 
until  the  vacuum  starts  to  form.     When  cool,  the  stopper  should 


AIR:   ANALYTICAL   METHODS  27 

project  at  least  one-half  an  inch  in  order  to  be  easily  removed. 
A  number  of  bottles  can  be  prepared  in  the  laboratory,  and  quite 
easily  transported.  All  rubber  stoppers  which  are  used  should 
first  be  boiled  in  dilute  caustic  soda,  then  in  a  dilute  solution  of 
potassium  bichromate  and  sulphuric  acid  and  thoroughly 
rinsed. 

To  collect  the  sample  it  is  necessary  only  to  remove  the  stopper, 
taking  care  to  hold  the  bottle  away  from  the  face  in  order  to 
prevent  contamination  from  the  carbon  dioxide  of  the  breath. 

At  the  time  of  collecting  the  samples  the  following  observations 
should  be  recorded:  room,  date,  time,  weather,  place  in  room, 
number  of  people  present,  number  of  gas  jets  or  lamps  burning, 
number  of  doors,  windows  and  transoms,  methods  of  heating 
and  ventilation,  and  anything  else  which  would  tend  to  in- 
fluence the  amount  of  carbon  dioxide  present. 

In  collecting  samples,  care  must  be  taken  to  avoid  currents  of 
air  or  the  close  proximity  of  people.  Exact  duplicate  analyses 
can  be  obtained  only  in  empty  or  in  nearly  empty  rooms.  Even 
two  sides  of  the  same  room  will  probably  show  differences,  but 
two  samples  taken  carefully  side  by  side  ought  to  agree  within 
0.05  part  per  10,000. 

Carbon  Dioxide.  —  The  most  accurate  analyses  of  air  have 
been  those  obtained  by  Benedict  by  means  of  an  apparatus 
especially  designed  by  Dr.  Klas  Sonden.*  The  analysis  de- 
pends upon  the  measurement  of  the  decrease  in  volume  of  a 
sample  of  air  after  contact  with  a  caustic  alkali  solution.  An- 
other accurate  apparatus  on  the  same  principle  is  that  of  Petter- 
sen-Palmquist,  f  which  has  been  modified  by  Rogers,  |  and 
more  recently  by  Anderson. §  In  all  of  these  forms  the  manipu- 
lation is  rather  delicate,  the  apparatus  is  bulky  to  transport, 
and  when  obtained,  the  results  are  much  more  accurate  than  is 
necessary  for  any  practical  work. 

*  A  description  of  this  will  be  found  in  Publication  No.  166,  Carnegie  Insti- 
tution of  Washington,  already  referred  to. 

t  For  description  see  Rosenau,  "  Hygiene  and  Preventive  Medicine." 
X  See  catalogue  of  Eimer  and  Amend. 
§  /.  Am.  Cliem.  Soc,  1913,  35,  p.  162. 


28  AIR,   WATER,   AND    FOOD 

Walker  Method.  —  The  method  to  be  most  recommended  for 
practical  analyses  for  carbon  dioxide  is  that  proposed  by  Walker.* 
It  has  been  carefully  studied  in  this  laboratory  f  and  slightly 
modified.     The  results  are  accurate  to  tenths  of  a  part  per  10,000. 

Principle.  —  To  a  definite  volume  of  air,  usually  one  to  two 
liters,  is  added  a  measured  amount  of  standard  barium  hydrox- 
ide, care  being  taken  to  avoid  contact  of  the  solution  with  the 
air.  After  the  absorption  of  the  carbon  dioxide,  the  solution  is 
filtered  under  reduced  pressure  through  asbestos  and  the  clear 
barium  hydroxide  received  into  a  known  excess  of  standard 
hydrochloric  acid.  The  absorption  bottle  is  rinsed  out  with 
water  free  from  carbon  dioxide.  The  excess  of  acid  is  then 
determined  by  titration  with  barium  hydroxide.  It  is  essential 
for  the  complete  absorption  of  the  carbon  dioxide  that  the  barium 
hydroxide  be  largely  in  excess,  so  that  not  more  than  one-fifth 
of  it  is  neutralized;  furthermore,  the  absorbing  solution  must  be 
shaken  with  the  air  for  a  considerable  time. 

Reagents  and  Apparatus.  —  The  standard  solutions  used  are 
N/50  hydrochloric  acid,  and  barium  hydroxide,  approximately 
N/ioo,  its  exact  strength  relative  to  the  acid  being  found  daily  by 
titration.  It  will  be  found  advantageous  to  use  solutions  of 
this  strength,  somewhat  more  dilute  than  those  recommended 
by  Walker,  on  account  of  the  increased  accuracy  with  air  nearly 
free  from  carbon  dioxide.  The  decreased  range  of  usefulness  is 
readily  compensated  by  the  employment  of  smaller  samples  of 
the  impure  air. 

The  barium  hydroxide  is  preserved  with  especial  care.  The 
hard-glass  bottle  containing  it,  placed  on  a  high  shelf  so  that 
the  measuring  apparatus  can  be  filled  directly  by  gravity,  is 
heavily  coated  on  the  inside  with  barium  carbonate.  The  bottle 
is  closed  by  a  rubber  stopper  with  two  holes,  one  of  which  car- 
ries the  siphon  tube  dipping  to  the  bottom  of  the  bottle  and 
supplying  the  measuring  burette,  while  the  other  carries  a  fairly 
large  glass  T.     (Fig.  3). 

*  J.  Chem.  Soc,  1900,  77,  p.  mo. 

t  Woodman,  /.  Afn.  Chem.  Soc,  1903,  25,  p.  150. 


AIR:    ANALYTICAL   METHODS 


29 


Fig.  3. 


From  one-half  the  horizontal  arm  of  this  projects  a  glass  tube 
carrymg  the  device  for  protecting  the  solution.  This  device  is 
shown  drawn  on  a  somewhat  larger  scale  in  the  same  sketch. 
The  horizontal  tube  enters  the  T  tube 
far  enough  to  support  the  apparatus. 
Connection  is  made  by  a  closely-fitting 
rubber  tube.  The  longer  tube,  reach- 
ing nearly  to  the  bottom  of  the  test- 
tube,  carries  a  fairly  good-sized  cal- 
cium-chloride tube  which  contains 
soda-lime,  enclosed  in  the  usual  man- 
ner by  plugs  of  cotton.  The  test-tube 
contains  five  to  10  c.c.  of  dilute  (about 
N/50)  caustic  potash  colored  with  phe- 
nolphthalein,  the  whole  serving  to  in- 
dicate the  efficiency  of  the  soda-lime. 
From  the  other  end  of  the  horizontal 
arm  of  the  T  projects,  in  the  same  way,  a  long  tube  bent  at 
right  angles  fitting  by  a  rubber  stopper  into  the  top  of  the 
burette,  thus  making  the  whole  a  closed  system,  much  after 
the  manner  of  Blochmann.*  Any  air  entering  the  bottle  when 
the  solution  is  drawn  from  the  burette  or  when  the  burette 
is  filled  again  must  have  come  through  the  protecting  appa- 
ratus. This  will  be  found  efficient  if  care  is  taken  in  the  selec- 
tion or  preparation  of  the  soda-lime.f 

The  burette  used  for  the  barium  hydroxide  is  a  glass-stop- 
pered one,  differing  somewhat  from  the  ordinary  form.  The 
portion  below  the  graduations  is  narrowed  and  bent  at  a  right 
angle.  This  horizontal  part  is  fitted  with  an  ordinary  glass 
stop  cock.  This  gives  no  trouble  when  kept  well  vaselined. 
The  tip  of  the  burette  is  kept  covered  with  a  little  rubber  cap 
when  not  in  use,  to  prevent  clogging  from  the  formation  of 
carbonate.      The  apparatus  could  easily  be  arranged  with   a 

*  Ann.  Chem.,  (Liebig),  1887,  237,  p.  39. 

t  Directions  for  preparing  a  good  quality  of  soda-lime  are  given  by  Benedict 
and  Tower,  7.  Am.  CJicm.  Soc,  1899,  21,  p.  396. 


3° 


AIR,   WATER,   AND    FOOD 


special  pipette  for  the  delivery  of  a  definite  charge  of  a  baryta 
solution. 

The  apparatus  used  for  filtering  off  the  barium  carbonate  is 
shown  in  Fig.  4.  On  the  base  of  a  ring  stand  is  placed  an  ordi- 
nary filter  bottle  of  about  250  c.c.  capacity  closed  by  a  rubber 
stopper  with  one  hole.     The  suction  pump  is  connected  with  the 

tube  on  the  side  of  the  bottle.  A  Gooch 
filtering-funnel,  the  upper  part  of 
which  is  cut  off  so  that  the  remainder 
above  the  constriction  is  about  an 
inch  long,  is  put  through  the  rubber 
stopper.  The  tip  projecting  into  the 
bottle  is  bent  so  that  the  liquid  shall 
flow  down  the  side  and  not  spatter. 
A  rather  close  coil  of  stout  platinum 
wire  placed  above  the  narrow  portion 
serves  as  a  support  for  an  asbestos 
filter.  A  two-cm.  Gooch  filter  plate 
serves  as  well  as  the  platinum  wire. 
In  the  upper  part  of  the  tube  is  a 
tightly-fitting  rubber  stopper,  through 
which  passes  a  narrow  glass  tube 
extending  to  within  one-eighth  inch 
of  the  asbestos  layer,  and  provided 
above  the  stopper  with  a  stop  cock. 
Connection  is  made  with  the  short 
tube  of  the  inverted  bottle  by  means 
of  a  rubber  tube  about  4  inches  in  length. 

The  inverted  bottle  is  a  carefully  calibrated  one  of  about 
one  liter  capacity,  and  is  used  for  collecting  the  sample,  the 
method  preferably  being  by  water  displacement  as  described 
on  page  25.  Record  the  temperature  and  barometric  pressure 
at  the  time  the  sample  is  taken.  After  collecting  the  sample  the 
bottle  is  closed  by  a  solid  rubber  stopper.  For  filtering,  this  is 
replaced  by  a  rubber  stopper  through  which  pass  two  glass 
tubes.     The  longer  tube  reaches  nearly  to  the  bottom  of  the 


Fig.  4. 


AIR:   ANALYTICAL   METHODS  31 

bottle,  is  bent  as  shown,  and  contains  a  glass  stop  cock.  The 
shorter  tube  ends  internally  just  flush  with  the  stopper,  and  out- 
side is  fitted  with  a  stop  cock  and  projects  just  far  enough  to 
make  connection  with  the  rubber  tubing.  The  glass  stop  cocks 
may  be  replaced  by  rubber  tubing  and  Mohr  pinch  clamps. 

The  filter  is  made  of  washed  asbestos,  free  from  acids,  in  the 
manner  usual  for  Gooch  crucibles.  The  same  filter  will  do  for 
a  number  of  determinations.  The  asbestos  layer  should  be 
about  one-eighth  of  an  inch  thick  and  should  be  washed  with 
distilled  water. 

Procedure.  —  Remove  the  stopper  from  the  cahbrated  bottle 
containing  the  sample  of  air,  and  run  in  rapidly  from  the  burette 
about  25  c.c.  of  the  barium  hydroxide  solution,  the  exact  amount 
being  determined  from  the  burette  readings.  Immediately  re- 
place the  rubber  stopper,  place  the  bottle  on  its  side  and  shake 
at  very  frequent  intervals  for  20  minutes,  giving  a  sort  of  rotat- 
ing motion  so  that  the  solution  will  spread  over  the  bottle,  and 
thus  expose  a  large  surface  for  absorption  of  the  carbon  dioxide. 

While  the  absorption  is  going  on  prepare  the  filter  (although 
it  is  better  to  prepare  this,  and  to  standardize  the  barium  hydrox- 
ide before  starting  the  determination)  and  also  make  about 
100  c.c.  of  wash  water  for  each  determination.  This  latter  is 
done  by  adding  to  distilled  water  one  c.c.  of  a  10  per  cent 
barium  chloride  solution  and  three  drops  of  phcnolphthalein, 
then  titrating  with  the  barium  hydroxide  to  a  faint  permanent 
pink.     Keep  in  a  stoppered  flask  until  wanted. 

Standardize  the  barium  hydroxide  against  the  hydrochloric 
acid  in  the  usual  manner.  Employ  some  wash  water  for 
diluting  in  place  of  distilled  water,  which  contains  some  carbon 
dioxide. 

Measure  into  the  filter  bottle  from  a  burette  about  13  c.c.  (or 
an  amount  slightly  more  than  equivalent  to  the  barium  hydrox- 
ide used)  of  N/50  hydrochloric  acid,  the  exact  amount  being 
obtained  from  the  burette  readings. 

After  the  absorption  is  finished  remove  the  rubber  stopper 
from  the  bottle,  and  wash  the  stopper  with  a  Httle  of  the  wash 


32  AIR,   WATER,   AND    FOOD 

water,  letting  the  washings  run  into  the  bottle.  Insert  the  two- 
hole  rubber  stopper  with  connections  for  filtering  and  invert  as 
shown  in  the  figure. 

Open  the  upper  stop  cock  and  turn  on  the  pump.  Now  slowly 
open  the  filter  stop  cock  and  control  the  flow  of  liquid  entirely 
with  this  cock.  The  barium  carbonate  remains  on  the  asbestos, 
and  the  clear  baryta  solution  which  passes  through  is  at  once 
neutralized  by  the  hydrochloric  acid.  When  all  the  hquid  has 
passed  through  allow  the  pump  to  act  for  a  few  minutes  until 
the  bottle  is  partially  exhausted,  then  close  the  filter  cock. 

Pour  some  of  the  wash  water  into  a  small  beaker,  dip  the  end 
of  the  longer  tube  into  it,  and  by  opening  the  stop  cock  allow 
about  20  c.c.  to  flow  into  the  bottle  before  closing  it.  Un- 
clamp  the  bottle  and  shake  thoroughly  while  held  horizontally 
and  still  attached  to  the  filter.  Clamp  it  in  place  again,  turn  on 
the  pump,  and  draw  the  wash  water  through  the  filter.  Repeat 
this  twice.  Generally  at  the  third  washing  the  wash  water  no 
longer  turns  pink,  showing  that  the  barium  hydroxide  has  been 
completely  removed.     If  the  pink  color  persists  wash  again. 

Remove  the  filter  bottle  and  titrate  in  the  bottle,  for  the  ex- 
cess of  acid,  with  barium  hydroxide.  The  end  point  is  a  distinct 
pink  which  is  permanent  for  one  minute. 

To  obtain  the  amount  of  carbon  dioxide  subtract  the  number 
of  cubic  centimeters  of  N/50  acid  used  from  the  number  of  cubic 
centimeters  of  acid  equivalent  to  the  barium  hydroxide  used. 
This  will  give  the  amount  of  carbon  dioxide  in  the  sample  in 
terms  of  N/50  acid,  from  which  the  actual  number  of  grams  of 
carbon  dioxide  can  be  obtained.  From  the  table  in  the  ap- 
pendix *  obtain  the  weight  of  one  cubic  centimeter  of  carbon 
dioxide  for  the  conditions  of  temperature  and  pressure  observed 
when  the  sample  was  taken.  From  this  the  volume  of  carbon 
dioxide  in  the  sample  can  be  calculated,  and  knowing  the  vol- 
ume of  the  bottle,  and  making  allowance  for  the  25  c.c.  of  alkali 

*  Dietrich's  Table,  the  one  in  general  use,  is  not  absolutely  correct,  the  weight 
of  a  cubic  centimeter  of  carbon  dioxide  at  0°  C.  and  760  mm.  being  somewhat 
different  from  that  given  at  present  by  the  best  authorities,  but  it  is  sufficiently 
close  for  any  but  the  most  exacting  work. 


AIR:  ANALYTICAL  METHODS  33 

added,  the  parts  of  carbon  dioxide  per  10,000  of  air  can  be 
calculated. 

A  sample  calculation  follows: 

Standardization:  —  i  c.c.  Ba(0H)2  =  0.48  c.c.  N/50  HCl. 
Volume  of  bottle  =  991  c.c.     Temperature  =  18°  C.     Ba- 
rometer =  764  mm. 
Total  Ba(0H)2  used  58.02.     HCl  used  =  26.08. 
58.02  c.c.  Ba(0H)2  =  58.02  X  0.48  =  27.85  c.c.  HCl. 
27.85  —  26.08  =  1.77  c.c.  N/50  acid  equivalent  to  the  CO2 

present. 
Since   i  c.c.   N/50    acid  =  0.44  mg.    CO2,  then  there    are 

present  in  the  sample  0.78  mg.  CO2. 
I  c.c.  CO2  at  18''  and  764  mm.  weighs  1.817  mg.     .".  991  — 
25  =  966  c.c.  of  air  contains  .429  c.c.  CO2  or  4.4  pts.  CO2 
per  10,000. 
If  the  amount  of  carbon  dioxide  present  exceeds  25  parts  per 
10,000,  either  a  500  c.c.  bottle  may  be  used  for  collecting  the 
samples,  or  double  the  quantities  of  barium  hydroxide  and  hydro- 
chloric acid  should  be  added.     Such  a  condition  rarely  exists 
in  practical  work. 

Pettenkofer  Method.  —  The  method  which  for  many  years 
was  generally  employed  for  the  estimation  of  carbon  dioxide  in 
the  air  of  rooms  is  a  modification  of  that  originally  devised  by 
Pettenkofer,*  While  this  method  is  convenient,  and  for  a  long 
time  has  been  the  favorite,  it  is  now  quite  generally  recognized 
that  it  contains  inherent  sources  of  error  which  can  be  obviated 
only  by  the  use  of  complicated  apparatus  and  extreme  skill  in 
manipulation.  It  should,  therefore,  be  borne  in  mind  that  the 
results  obtained  are  generally  too  high  even  though  agreeing 
closely  among  themselves. 

Principle.  —  The  principle  is  essentially  the  same  as  that  of 
the  Walker  method,  i.e.,  the  absorption  of  carbon  dioxide  from 
a  known  volume  of  air  in  barium  hydroxide  solution  and  the 
titration  of  the  excess  with  standard  sulphuric  acid. 

*  Pettenkofer,  Annalen,  2,  Supp.  Band,  1862,  p.  i;  Gill,  Aiulyst,  1892,  17, 
p.  184. 


34  AIR,   WATER,  AND   FOOD 

The  samples  are  collected  in  four-  or  six-liter  bottles,  as  de- 
scribed on  page  24,  each  provided  with  a  rubber  stopper  carry- 
ing a  glass  tube  over  which  a  rubber  nipple  or  cap  is  slipped. 
Note  particularly  the  temperature  and  barometric  pressure. 

Reagents  and  Apparatus.  —  The  solutions  used  are  sulphuric 
acid  of  such  a  strength  that  one  c.c.  equals  one  milligram  of 
carbon  dioxide  (see  appendix  B),  and  barium  hydroxide  solu- 
tion of  approximately  equal  strength.  Since  it  is  impracticable 
to  prepare  exact  solutions  of  barium  hydroxide,  and  to  keep 
them  without  change,  the  exact  value  of  the  barium  hydroxide 
solution  must  be  found  by  titration  against  the  standard  sul- 
phuric acid.  This  standardization,  as  well  as  the  subsequent 
titration,  is  best  made  in  a  small  flask  to  lessen  the  error  from 
absorption  of  carbon  dioxide  from  the  air.  It  will  be  found 
most  generally  satisfactory  to  measure  into  the  flask  about  25 
c.c.  of  the  barium  hydroxide,  add  a  drop  of  phenolphthalein 
solution,  and  titrate  with  the  sulphuric  acid  to  the  disappear- 
ance of  the  pink  color.  In  all  cases  the  first  end-point  should 
be  taken  as  the  correct  one,  because  the  pink  color  will  some- 
times return  on  standing. 

The  apparatus  consists  of  the  collecting  bottles,  50  c.c.  bu- 
rettes, a  stoppered  bottle  of  hard  glass  of  40  c.c.  capacity,  and 
a  25  c.c.  pipette. 

Procedure.  —  Remove  the  cap  from  the  tube  in  the  stopper 
of  the  bottle,  insert  the  tip  of  the  burette  so  that  it  projects  into 
the  bottle,  and  run  in  rapidly  50  c.c.  of  barium  hydroxide  from 
the  burette.  Replace  the  cap,  place  the  bottle  on  its  side  and 
roll  or  shake  it  at  frequent  intervals  for  45  minutes,  taking  care 
that  the  whole  surface  of  the  bottle  is  moistened  with  the  solu- 
tion each  time.  At  the  end  of  this  time  thoroughly  shake  the 
bottle  to  mix  the  solution,  remove  the  cap,  and  pour  the  solu- 
tion into  a  stoppered  bottle  of  hard  glass  of  40  c.c.  capacity, 
taking  care  that  the  solution  shall  come  in  contact  with  the  air 
as  little  as  possible.  Under  these  conditions  a  full  well-stoppered 
bottle  may  safely  stand  for  days  before  titration.  For  the 
titration,  measure  out  with  a  pipette  25  c.c.  of  the  clear  liquid 


AIR:   ANALYTICAL   METHODS  35 

into  a  75  c.c.  flask  and  titrate  it  with  the  sulphuric  acid  as  in 
the  standardization. 

The  calculation  is  similar  to  that  given  under  the  Walker 
method  except  that  it  should  be  remembered  that  only  one- 
half  of  the  barium  hydroxide  was  used  in  the  titration. 

Rapid  Methods.  —  In  addition  to  the  above  methods  for  de- 
termining carbon  dioxide  just  described,  there  are  general  tests 
which  can  often  be  used  with  advantage.  If  within  the  space 
of  a  few  hours  some  50  or  more  tests  are  to  be  made,  and  com- 
parative results  rather  than  great  accuracy  are  required,  some 
simpler  form  of  apparatus  is  desirable. 

Such  an  apparatus,  to  be  satisfactory,  should  meet,  so  far  as 
possible,  the  following  requirements: 

(i)  It  should  be  sufficiently  compact  and  portable  to  be  car- 
ried in  the  hand  from  place  to  place. 

(2)  It  should  be  as  simple  in  construction  as  possible,  and  its 
use  should  not  involve  delicate  measurements. 

(3)  If  possible,  the  apparatus  should  be  made  entirely  of  glass, 
avoiding  prolonged  contact  of  corks  or  of  rubber  connectors 
with  any  dilute  solution  which  may  be  used. 

(4)  It  should  be  so  constructed  as  to  protect  the  solution  at 
all  times  from  the  carbon  dioxide  of  the  air,  especially  whOe  the 
determination  is  being  made,  because  of  necessity  such  an  ap- 
paratus must  be  used  within  the  area  of  contamination. 

(5)  The  complete  apparatus  should  be  sufiicient  for  50  or 
more  determinations. 

(6)  It  must  be  capable  of  giving  results  of  a  reasonable  de- 
gree of  accuracy,  say  within  0.5  part  of  carbon  dioxide  in  10,000 
parts  of  air,  in  the  hands  of  persons  having  little  or  no  chemical 
knowledge  and  minimum  skill  in  manipulation. 

(7)  If  a  solution  be  used  in  the  apparatus  it  should  be  one 
which  can  be  prepared  easily  from  chemicals  readily  obtained; 
the  solution  must  maintain  its  efficiency  for  a  reasonable  length 
of  time,  if  protected  from  external  influences;  and  the  solution 
should  be  one  that  is  not  at  all  dangerous  or  obnoxious  to  use. 

Simplicity  of  apparatus  is  much  to  be  desired,  but  it  should 


36 


AIR,   WATER,   AND    FOOD 


not  be  gained  at  too  great  sacrifice  of  accuracy.  Even  when  no 
greater  precision  is  required  than  is  necessary  to  meet  the  de- 
mands of  practical  work,  it  is  out  of  the  question  to  measure  the 
test  solution  by  means  of  an  ordinary  pipette  or  to  preserve  it 
for  any  length  of  time  in  stoppered  vials;  the  strength  of  the 
solution  is  almost  certain  to  be  reduced  by  contamination  with 
the  breath,  or  by  contact  with  rubber  or  cork. 

It  must  ever  be  borne  in  mind  that  extreme  care  is  necessary 
in  the  preparation  and  use  of  these  very  dilute  solutions,  the 
strict  observance  of  conditions  which  might  well  be  neglected 
in  ordinary  analytical  procedures  being  here  an  essential  factor 
of  success. 

For  the  preservation  and  measuring  of  the  test  solution  an 
apparatus  has  been  devised  which  appears  to  answer  the  above 
requirements,  and  in  actual  practice  has  been  found  satisfactory.* 

The  essential  feature  of  this 
apparatus  consists  of  an  auto- 
matic pipette  for  measuring 
the  test  solution.  This  is  a 
modified  form  of  the  pipette 
first  proposed  by  G.  P.  Vanier 
and  in  use  in  this  laboratory 
for  a  number  of  years.  A 
general  idea  of  it  may  be  had 
from  Fig.  5.  The  manner  of 
using  it  is  extremely  simple. 
The  test  solution  is  preserved 
in  a  one-liter  bottle  of  hard 
glass  provided  with  a  doubly 
perforated  rubber  stopper. 
Through  one  opening  passes 
the  siphon  tube  of  the  pipette,  which  is  sufficiently  long  to  reach 
to  the  bottom  of  the  bottle;  through  the  other  passes  a  glass 
tube  ending  just  below  the  stopper  and  connected  with  a  small 

*  "Air  Testing  for  Engineers,"  A.  G.  Woodman  and  Ellen  H.  Richards,  Tech. 
Quay.,  1901,  14,  p.  94. 


Fig.  5. 


AIR:   ANALYTICAL    METHODS  37 

drying  tube  containing  fresh  soda-lime.  By  means  of  the  three- 
way  cock  the  solution  is  allowed  to  flow  into  the  small  inside 
pipette  until  it  overflows.  The  stop  cock  is  then  turned,  and 
the  solution  allowed  to  flow  out  at  the  lowest  point.  The  pipette 
is  made  of  such  a  size  as  to  deliver  exactly  lo  c.c.  The  excess 
of  liquid  which  accumulates  in  the  ov^erflow  reser\'oir  may  be 
drawn  off  when  desired.  The  bottle  and  pipette  are  contained 
in  a  wooden  case,  about  20  by  8  by  7  inches,  outside  dimen- 
sions, and  with  the  solution,  weigh  about  eight  pounds.  The 
case  is  furnished  with  a  handle  at  the  top  so  that  it  may  be 
carried  readily  in  the  hand  from  place  to  place.  The  bottle 
is  fastened  to  the  case,  and  the  lower  end  of  the  pipette  is 
clamped  to  a  wooden  support  to  keep  it  from  swinging.  The 
stopper  should  be  firmly  fastened  to  prevent  loosening. 

The  bottle  should  be  thoroughly  cleaned  and  washed  with 
potassium  bichromate  and  sulphuric  acid,  and  it  is  best  also  to 
steam  it  for  half  an  hour  or  so.  As  a  further  measure  of  pre- 
caution the  rubber  stopper  is  boiled  with  dilute  caustic  potash 
and  thoroughly  washed,  although  the  solution  can  come  in  con- 
tact with  it  only  through  splashing  while  the  case  is  being 
carried. 

This  measuring  apparatus  may  be  used  with  a  variety  of 
methods,  and  with  various  strengths  of  solution. 

Cohen  and  Appleyard  Method.*  —  Principle.  —  The  method 
of  Cohen  and  Appleyard  is  based  upon  the  fact  that  if  a  dilute 
solution  of  lime-water,  slightly  colored  with  phenolphthalcin,  is 
brought  in  contact  with  a  sample  of  air  containing  more  than 
enough  carbon  dioxide  to  combine  with  all  the  lime  present,  the 
solution  will  be  gradually  decolorized,  the  length  of  time  re- 
quired depending  upon  the  amount  of  carbon  dioxide  present. 
That  is,  the  quantity  of  lime-water  and  the  volume  of  air  re- 
maining the  same  in  each  case,  the  rate  of  decolorization  will 
vary  inversely  with  the  amount  of  carbon  dioxide. 

Reagents  and  Apparatus.  — The  solution  used  is  a  dUute  so- 
lution of  lime-water  colored  with  phenolphthalcin.  To  freshly 
*  Chcm.  News,  1894,  70,  p.  iii. 


38  AIR,  WATER,  AND   FOOD 

slaked  lime  add  20  times  its  weight  of  water  in  a  bottle  of  such 
size  that  it  is  not  more  than  two-thirds  full.  Shake  the  mix- 
ture continuously  for  20  minutes,  and  then  allow  it  to  settle 
over  night  or  until  perfectly  clear.  The  resulting  solution  is  the 
stock  lime  solution,  or  "  saturated  lime-water."  If  made  in  the 
manner  indicated,  each  cubic  centimeter  of  it  ought  to  be  very 
nearly  equivalent  to  one  milligram  of  carbon  dioxide.  If,  how- 
ever, it  is  desired  to  know  the  strength  of  it  more  exactly,  it 
may  be  determined  by  standard  acid. 

To  prepare  the  "  test  solution,"  pour  into  the  one-liter  bottle 
of  the  testing  apparatus  one  measured  liter  of  distilled  water, 
and  add  2.5  c.c.  of  a  solution  of  phenolphthalein  (made  by  dis- 
solving 0.7  gram  of  phenolphthalein  in  50  c.c.  of  alcohol  and 
adding  an  equal  volume  of  water).  Stand  the  bottle  on  a  sheet 
of  white  paper  and  add  the  ''  saturated  lime-water  "  drop  by 
drop  from  a  pipette,  shaking  the  bottle  thoroughly  after  each 
addition  until  a  faint  pink  color  is  produced  which  is  permanent 
for  one  minute.  Now  add  6.3  c.c.  of  the  ''saturated  lime-water," 
shake,  and  immediately  connect  the  bottle  again  to  the  apparatus. 

For  accuracy  in  air  which  is  high  in  carbon  dioxide,  it  is  found 
advantageous  to  use  a  solution  which  is  twice  as  strong  as  the 
above.  This  double  solution  is  prepared  in  precisely  the  same 
way,  using  5.0  c.c.  of  the  phenolphthalein  solution  and  12.6  c.c. 
of  the  "  saturated  lime-water." 

While  this  procedure  does  not  give  an  exact  volume  of  solu- 
tion, it  is  believed  to  be  the  best  for  the  preparation  of  this 
dilute  test  solution,  since  it  obviates  the  necessity  for  pouring 
the  prepared  solution  from  the  measuring  flask  into  the  bottle 
in  which  it  is  kept;  12.6  c.c.  of  the  stock  lime  solution  is  added 
rather  than  10  c.c,  in  order  to  keep  the  values  obtained  with 
the  resulting  solution  more  nearly  comparable  with  the  older 
values  calculated  on  the  supposition  that  10  c.c.  of  the  "  satu- 
rated lime-water  "  was  equivalent  to  12.6  mg.  of  carbon  dioxide. 

The  apparatus  used  is  that  shown  in  Fig.  5.  The  samples  are 
collected  in  500  c.c.  bottles  by  either  the  water  displacement  or 
steam  vacuum  method. 


AIR:   ANALYTICAL   METHOD 


39 


Procedure.  —  Remove  the  rubber  stopper  from  the  bottle  con- 
taining the  sample  of  air;  run  in  quickly  by  means  of  the  auto- 
matic pipette  lo  c.c.  of  the  standard  test  solution;  note  the 
time;  replace  the  stopper;  shake  continuously  and  vigorously 
until  the  pink  color  disappears;  and  again  note  the  time.  The 
disappearance  of  color  can  most  easily  be  seen  if  the  bottle  is 
held  over  a  piece  of  white  paper.  From  the  time  required  for 
the  pink  color  to  disappear,  the  amount  of  carbon  dioxide  may 
be  found  from  Table  A. 

TABLE  A 


Time, 
minutes 

and 
seconds. 

Standard 

solution. 

CO2  in 

10,000. 

Double 

solution. 

COjin 

10,000. 

Time, 
minutes 

and 
seconds. 

Double 

solution. 

COjin 

10,000. 

O.IS 
0.30 

0.45 
1 .00 

IIS 
1.30 
1-45 
2.00 

2. IS 
2.30 

2.4s 
3.00 

31S 

3-45 
4.00 

41S 
430 
4-45 
5.00 

S15 
S-30 

"iS-6' 
12. 1 
9.9 
8.4 

7.2 

6.3 

ss 

4-9 
4-4 
4.0 
3-8 
3-7 
3-6 

S-45 
6.00 

6.15 
6.30 

6.4S 
7.00 

71S 
7-3° 

1 

4.0 
3-9 

3-7 

16 

13 
II 
10 

9 

8 

7 
7 
6 
6 
S 
5 
5 
4 
4 
4 
4 
4 
4 

0 

I 

4 
I 

I 

3 
6 
0 

5 
I 

7 
4 

I 

9 

7 
S 
3 

2 
I 

Shaker  Methods.  —  At  least  two  forms  of  apparatus  are  on 
the  market  for  determining  the  percentage  of  carbon  dioxide  by 
measuring  the  amount  of  air  required  to  decolorize  the  stand- 
ard solutions  described  on  page  38.  These  are  known  as  the 
Fitz  and  the  Wolpert  Shakers  (see  Fig.  6).  The  results  obtained 
are  less  accurate  and  more  uncertain  than  by  other  methods, 
but  if  great  care   is  taken    to   keep  the   apparatus   at    some 


40 


AIR,   WATER,  AND   FOOD 


distance  from  the  face  of  the  worker,  approximate  results  can 
be  obtained.  As  both  shakers  operate  on  the  same  principle 
only  the  Fitz  will  be  described.  It  consists  of  a  tube  of  about 
30  c.c.  capacity,  closed  at  one  end,  and  graduated  for  a  dis- 
tance of  20  c.c.  from  the  closed  end.  In  this 
tube,  by  means  of  a  rubber  collar,  slides  a  smaller 
tube  which  is  contracted  at  the  outer  end  so  as 
to  be  more  readily  closed  by  the  linger. 

Procedure.  —  See  that  the  inner  tube  of  the 
shaker  slides  readily  in  the  outer  one,  moistening 
the  rubber  collar  slightly  if  necessary.  Have 
the  inner  tube  pressed  down  to  the  bottom  of 
the  larger  one  and  measure  into  the  apparatus 
10  c.c.  of  the  test  solution  from  the  automatic 
pipette.  Pull  the  inner  tube  up  to  the  5  c.c. 
mark  (the  bottom  of  the  inner  tube  serving  as 
the  index)  and  close  the  end  of  the  tube  with 
the  finger.  Hold  the  apparatus  horizontally, 
and  shake  it  vigorously  for  exactly  30  seconds. 
The  amount  of  air  that  is  thus  brought  in  contact  with  the 
solution  is  equivalent  to  approximately  30  c.c,  as  there  are 
25  c.c.  of  air  above  the  liquid  when  the  small  tube  is  forced  to 
bottom  of  the  larger.  Remove  the  finger,  press  down  the  small 
tube  again  to  the  bottom  of  the  larger  and  draw  it  up  to  the 
20  c.c.  mark.  Shake  the  apparatus  again  for  30  seconds.  The 
amount  of  air  brought  in  contact  with  the  solution  is  now 
30  +  20  =  50  c.c.  Repeat  the  shaking,  using  20  c.c.  of  fresh 
air  each  time,  until  the  pink  color  is  discharged.  The  amount 
of  carbon  dioxide  corresponding  to  the  number  of  cubic  centi- 
meters of  air  used  will  be  found  in  Table  B. 

Carbon  Monoxide.  —  The  detection  and  estimation  of  carbon 
monoxide  in  the  very  minute  quantities  in  which  it  is  found  in 
the  air  of  ordinary  rooms  is  a  problem  of  considerable  difficulty. 
Detection.  —  Probably  the  most  convenient  test  for  detecting 
small  quantities  is  the  blood  test.  Dilute  a  large  drop  of  human 
blood,  freshly  drawn  by  pricking  the  finger,  to  10  c.c.  with  water. 


Fig.  6.     Fitz 
Shaker 


AIR:    ANALYTICAL    METHODS 


41 


Divide  the  solution  into  two  equal  portions,  and  shake  one 
portion  gently  for  10  minutes  in  a  bottle  containing  about 
100  c.c.  of  the  air  to  be  tested.  Compare  the  tints  of  the  two 
portions  by  holding  them  against  a  well-lighted  white  surface. 
The  presence  of  carbon  monoxide  is  indicated  by  the  appear- 

TABLE  B 


Cubic  centimeters 
of  air. 

Standard  test 
solution. 

Double 

solution. 

COj  in  10,000. 

CO2  in  10,000. 

SO 

15-6 

22.2 

70 

12.4 

18 

0 

90 

10.2 

IS 

I 

no 

8.7 

13 

0 

13'^ 

7-5 

II 

3 

150 

6.6 

9 

9 

170 

5-8 

8 

8 

190 

5-2 

8 

0 

210 

4.8 

7 

3 

230 

4-S 

6 

8 

250 

4-3 

6 

3 

270 

41 

5 

9 

290 

3-95 

S 

6 

310 

3-8 

5 

4 

330 

3-7 

S 

I 

350 

3-6 

4 

8 

370 
390 
410 

4 
4 
4 
4 
4 
3 

7 
S 
4 
2 

45° 
490 

530 

0 

9 

ance  of  a  pink  tint  in  the  blood  which  has  been  shaken  with  air. 
One  part  in  10,000  can  be  detected  in  this  way.*  The  dcHcacy 
of  the  test  can  be  increased  by  examining  the  blood,  after  shak- 
ing with  air,  with  a  spectroscope.  By  collecting  the  sample  in  a 
eight-liter  bottle  and  examining  it  in  this  way  o.oi  part  in  10,000 
may  be  detected. 

Determination.  —  Practically  all  the  methods  for  the  dctcmii- 
nation  of  carbon  monoxide  in  small  amounts  depend  on  the 
equation: 

l205-t-5CO->5CO>  +  L; 

*  Clowes,  "Detection  and  Estimation  of  Inflammable  Gas  and  \'apor  in  the 
Air,"  p.  138. 


42  AIR,   WATER,  AND   FOOD 

then  either  the  iodine  *  is  titrated  or  the  carbon  dioxide  deter- 
mined. The  method  consists  of  passing  the  air  through  U-tubes 
containing  potassimn  hydroxide  and  sulphuric  acid  to  remove 
unsaturated  hydrocarbons,  hydrogen  sulphide,  etc.,  and  then 
through  a  U-tube  containing  iodine  pentoxide,  and  heated  to 
150°  C.  The  iodine  liberated  is  absorbed  in  a  solution  of  potas- 
sium iodide,  and  may  be  titrated  with  N/iooo  sodium  thiosul- 
phate,  or  the  carbon  dioxide  passing  through  the  potassium 
iodide  may  be  absorbed  by  barium  hydroxide  and  determined. f 

Nitrites.  — ■  The  determination  of  the  amount  of  nitrites  or 
nitrous  acid  in  the  air  can  be  readily  made  as  follows:  Collect 
a  sample  of  the  air  in  a  calibrated  eight-liter  bottle,  as  in  the 
determination  of  carbon  dioxide.  Add  100  c.c.  of  approxi- 
mately N/50  sodium  hydroxide  solution.  (This  should  be  free 
from  nitrites,  and  is  best  made  by  dissolving  metallic  sodium 
in  redistilled  water.)  Shake  the  bottle  occasionally  and  let  it 
stand  for  about  24  hours.  Take  out  50  c.c.  of  the  solution  and 
determine  the  amount  of  nitrites  as  directed  in  the  determination 
of  nitrites  in  water. 

Micro-organisms.J  —  The  determination  of  bacteria  in  the 
air  is  of  importance  only  under  special  conditions  which  some- 
times exist  in  dairies,  factories,  etc.  In  general  the  method  used 
is  to  filter  a  measured  amount  of  air  through  sand,  shake  out 
the  bacteria  with  sterile  water,  and  plate  aliquot  portions. 
Counts  are  made  after  5  days'  incubation  at  20°  C. 

*  Kinnicutt  and  Sanford,  J.  Am.  Chem.  Soc,  1900,  22,  p.  14. 
Morgan  and  McWhorter,  J.  Am.  Chem.  Soc,  1907,  29,  p.  1589. 
Seidell,  /.  Ind.  Eng.  Chem.,  1914,  6,  p.  321. 
Gautier,  J.  Gas  Lighting,  121,  p.  547. 
t  For  details  of  the  methods  reference  should  be  made  to  the  above  articles. 
Recently  a  portable  apparatus  has  been  described  by  Goutal,  Analyst,  19 10,  35, 
p.  130. 

X  See  "Standard  Methods  for  the  Bacterial  Examination  of  Air,"  Am.  J.  Pub. 
Health,  1910,  6,  No.  3,  or  reprint  by  the  Am.  Pub.  Health  Assn. 


CHAPTER   IV 
water:  its  relation  to  health,  its  sources  and  properties 

Two-thirds  of  the  animal  organism  consists  of  water;  this 
water  is  necessary  *  for  practically  all  physiological  processes, 
either  taking  part  in  the  reaction  or  acting  as  a  solvent.  It  aids 
in  carrying  nourishment  to  all  parts  of  the  body  and  in  disposing 
of  the  waste  products  formed.  The  evaporation  of  water  from 
the  surface  of  the  body  serves  as  the  most  important  method 
of  regulating  the  body  temperature.  Since  water  is  lost  by 
these  means  as  well  as  during  respiration,  it  is  evident  that  the 
animal  organism  must  be  supplied  with  water  from  outside 
sources.  The  daily  amount  needed  for  each  person  is  five  or 
six  pints.  This  water  is  derived  in  part  from  food  which,  as 
eaten,  contains  from  30  to  95  per  cent;  in  part  from  boiled 
water,  as  in  tea  and  coffee;  or  raw  from  well  or  city  tap. 

Water  is  also  required  for  many  other  purposes,  such  as  cook- 
ing, washing,  generation  of  power,  and  other  manufacturing 
uses.  It  has  been  estimated  that  25  gallons  per  person  per  day 
is  sufficient  for  household  purposes.  Then  some  must  be  al- 
lowed for  public  use  and  a  rather  large  amount  for  manufactur- 
ing. For  cities  in  this  country  amounts  varying  from  50  to 
200  gallons  are  used,  with  an  average  of  close  to  100  gallons. 
This  is  about  three  times  as  much  as  is  used  in  European  cities, 
and  undoubtedly  a  large  amount  represents  unnecessary  waste. 
That  this  is  true  is  shown  by  the  fact  that  when  the  individuals 
in  a  community  are  required  to  pay  for  the  actual  amount  of 
water  consumed,  which  is  done  through  the  introduction  of 
meters,  the  consumption  falls  off  to  one-half  or  one-third  of  the 
former  quantity  used.  Waste  of  water  represents  a  very  serious 
problem  in  large  cities,  where  it  is  often  necessary  to  go  long 

*  See  "  Text-book  of  Physiological  Chemistry,"  .\bderhalden-HaU,  John  Wiley 
&  Sons,  1908,  p.  354. 

43 


44  AIR,  WATER,  AND   FOOD 

distances  at  great  expense,  to  obtain  a  sufficiently  large  supply 
suitable  for  drinking  purposes. 

The  problem  is  made  still  more  difficult  by  the  use  of  large 
bodies  of  water,  both  lakes. and  rivers,  for  the  purposes  of  waste 
disposal.  Recent  reports  of  experts  *  have  raised  the  question 
as  to  how  much  of  the  expense  of  purifying  a  sewage  should  be 
borne  by  the  community  emptying  its  waste  into  a  stream,  and 
how  much  should  be  borne  by  a  community  farther  down  the 
stream  where  water  is  removed  for  domestic  use.  The  only 
certain  condition  which  should  be  demanded  is  that  wastes 
should  be  in  such  a  state  and  so  diluted  that  no  nuisance  will 
be  created  along  the  banks  of  the  stream.  It  seems  as  if  the 
question  of  further  purification  would  have  to  be  decided  for 
each  individual  case  as  it  arises. 

That  there  is  a  close  relation  between  drinking  water  and 
disease  has  long  been  suspected,  but  it  is  only  since  the  develop- 
ment of  the  present  ideas  of  the  cause  of  disease  that  this 
relationship  has  been  satisfactorily  demonstrated.  Drinking 
water  may  act  as  the  carrier  of  the  germs  of  at  least  two  well 
defined  diseases,  —  Asiatic  cholera  and  typhoid  fever,  —  and 
probably  of  those  of  other  intestinal  troubles.  There  is,  be- 
sides, some  tendency  to  disturb  the  system  when  a  change  is 
made  from  one  kind  of  drinking  water  to  another  of  radically 
different  composition,  such,  for  example,  as  a  change  from  a 
hard  Middle  West  water  to  a  soft  New  England  water.  The 
disturbance  is  generally  only  temporary,  as  the  system  becomes 
rapidly  accustomed  to  new  conditions. 

The  first  cholera  epidemic  to  be  traced  definitely  to  drinking 
water  was  that  in  London  in  1854,  which  centered  about  the 
Broad  Street  Pump,  and  the  investigation  of  which  was  thor- 
oughly carried  out  by  an  efficient  health  officer.  Since  then 
numerous  epidemics  have  been  traced  to  the  use  of  polluted 
water,  notably  that  of  Hamburg  in  1892-3. f 

*  See,  for  example,  Eng.  Rec,  191 2,  65,  p.  209. 

t  For  a  description  of  epidemics  of  both  cholera  and  typhoid  fever  see  Sedg- 
wick's "Sanitary  Science  and  Public  Health." 


WATER  45 

In  this  country  we  have  little  to  fear  from  cholera  on  account 
of  the  efficient  work  of  the  Public  Health  Service  at  our  ports, 
but  typhoid  fever  is  still  a  scourge  and  a  disgrace.  As  early  as 
1850  it  was  maintained  by  Budd  in  England  that  this  fever  was 
spread  by  drinking  water,  but  no  sufficient  evidence  was  pro- 
duced until  the  Lausen,  Switzerland,  epidemic  of  1872.  The 
first  large  epidemic  in  this  country  to  be  traced  to  water  was  that 
of  Plymouth,  Pa.,  in  1885,  in  which  about  1000  cases  resulted 
from  the  negligence  of  an  attendant  on  one  typhoid  patient. 
Since  that  time  numerous  small  and  large  epidemics  have  been 
traced  with  more  or  less  certainty  to  the  use  of  polluted  water. 

That  the  introduction  of  a  good  water  supply  in  place  of  a 
bad  one  results  in  a  marked  decrease  in  t}'phoid  fever  can  be 
readily  seen  by  almost  endless  lists  of  statistics  of  cities  and 
towns  which  have  cither  obtained  a  new  supply  or  have  intro- 
duced filters,  the  deaths  from  typhoid  being  from  one-half  to 
one-fifth  of  the  number  formerly  recorded  in  such  places.* 

Not  only  does  the  introduction  of  unpolluted  water  mean  a 
decrease  in  typhoid  fever,  but  there  seems  also  to  be  a  general 
increase  in  the  health  of  the  community.  This  effect  was 
noticed  at  about  the  same  time  by  ISIills  in  this  country  and 
Reincke  in  Germany,  and  is  known  as  the  Mills-Reincke  phe- 
nomenon. Hazen  attempted  to  formulate  a  mathematical  re- 
lationship between  the  decrease  in  typhoid  fever  and  that  in  all 
other  diseases,  but  the  result  is  merely  an  approximation.  This 
increase  in  the  general  health  may  be  due  to  increased  vitality 
by  the  elimination  of  one  disease.  It  has  been  recently  sug- 
gested that  since  tuberculosis  is  hable  to  follow  typhoid  fever, 
a  decrease  in  the  latter  would  account  for  a  decrease  in  the 
former. 

Safe  water,  is,  therefore,  one  of  the  necessary  requirements  of 
any  community,  large  or  small. 

Rain  Water.  —  Let  us  trace  the  cycle  through  which  water 
passes,  and  point  out  the  sources  of  supply,  and  the  methods  of 
contamination.    Water  vapor  rising  from  the  sea  and  land  con- 

*  See  Am.  J.  Pub.  Health,  1913,  3.  P-  1327- 


46  AIR,   WATER,   AND   FOOD 

denses  and  falls  to  the  earth  as  rain.  As  it  does  so,  ammonia, 
carbon  dioxide,  and  other  soluble  gases  are  absorbed,  and  dust 
and  living  organisms  are  collected.  As  soon  as  these  sub- 
stances are  removed  from  the  air,  the  rain  water  becomes  a 
very  pure  source  of  supply,  and  can  be  used  for  drinking  pur- 
poses if  properly  stored.  There  are  several  factors  to  be  ob- 
served in  this.  First,  there  should  be  no  connection  whatever 
between  the  storage  tank  and  any  drain  or  sewer  from  a  house 
or  barn.  More  than  one  case  of  typhoid  fever  has  resulted 
from  the  backing  up  of  sewage  through  an  overflow  pipe  into  a 
rain  water  tank.  Second,  no  metal  or  other  material  which 
is  injurious  to  health  should  be  used  in  building  such  a  tank, 
as  rain  water  is  soft  and  often  slightly  acid  and,  therefore, 
has  considerable  solvent  power  for  most  metals.  The  best  ma- 
terials to  use  are  cement,  slate,  or  stoneware;  lead  should  be 
absolutely  avoided,  and  zinc  will  not  last  any  length  of  time. 
Third,  there  should  be  some  method  of  wasting  the  first  rain 
that  falls,  in  order  not  to  load  the  storage  tank  with  dirt  and 
other  material  which  may  come  from  a  roof  or  collecting  shed, 
and  render  the  water  unpalatable.  Fourth,  there  should  be 
some  easy  means  of  cleaning  the  tank,  and  this  should  be  done 
at  frequent  intervals.  Rain  water  is  used  for  drinking  practi- 
cally only  in  tropical  regions. 

Surface  Waters.  —  Approximately  one-third  of  the  rain  evapo- 
rates again  from  the  surface  where  it  falls;  another  third  runs 
off  on  the  surface,  forming  streams,  rivers,  and  lakes,  finally 
reaching  the  ocean;  the  other  third  sinks  into  the  ground,  per- 
haps joining  the  surface  waters  underground,  coming  out  as 
springs  or  flowing  wells,  or  remaining  in  the  soil.  The  average 
rainfall  for  the  whole  United  States  is  about  36  inches,  varying 
in  different  parts  of  the  country  from  almost  nothing  to  60 
inches.  Thus  we  find  the  amount  of  water  with  which  we  have 
to  deal  is  very  variable,  depending  on  the  locality  and  the 
season.  Approximately  one-half  of  the  rainfall  finds  its  way 
finally  into  rivers,  either  running  off  on  the  surface,  or  entering 
from  underground. 


WATER  47 

Surface  waters  form  an  exceedingly  important  source  of 
supplies,  as  most  large  cities  fmd  them  necessary  on  account 
of  the  large  quantities  of  water  required.  Water  from  small 
streams  and  brooks  on  a  water  shed  may  be  collected  and  stored 
in  reservoirs.  This  method  is  considerably  used,  particularly  in 
hilly  regions,  and  if  proper  care  is  taken  to  prevent  any  pollution 
on  the  watershed,  sufficient  supplies  of  excellent  quahty  may  be 
obtained.  The  reservoirs  are  generally  uncovered,  and  should 
be  stripped  of  all  plant  life.  Surface  water,  if  unpolluted, 
usually  improves  on  storage. 

Where  it  is  not  possible  to  obtain  a  supply  in  this  manner, 
large  rivers  or  lakes  are  used.  These  are  nearly  all  subject  to 
more  or  less  pollution,  and  in  general  the  water  should  not 
be  used  unless  filtered  or  sterilized.  Some  self-purification  will 
take  place  in  such  bodies  of  water.*  The  most  important 
factor  in  such  purification  is  the  removal  of  bacteria  by  means 
of  sedimentation,  the  larger  particles  in  the  water  carrying 
bacteria  with  them  to  the  bottom  of  the  stream  where  the  patho- 
genic varieties  soon  die  out.  Thus  in  a  slow  moving  stream 
harmful  organisms  are  removed  more  quickly  than  in  a  rapidly 
moving  river.  Another  important  factor  is  the  exhaustion  of 
the  food  supply.  Also,  conditions  of  temperature  are  not  favor- 
able for  the  growth  of  many  bacteria,  and  it  is  undoubtedly 
true  that  even  in  a  highly  polluted  water  there  is  little  multi- 
plication, and  much  dying  off  of  disease  organisms. 

On  the  other  hand,  it  is  not  safe  to  rely  on  self-purification, 
particularly  when  the  health  of  a  large  number  of  people  is  at 
stake.  There  are  too  many  possibilities  of  accidental  pollution. 
Some  artificial  means  must  be  used.  These  will  be  mentioned 
later. 

Odors  sometimes  develop  in  stored  water  as  a  result  of  growth 
of  various  plants  and  animals.f     Some  of  these  odors  are  ex- 

*  See  Jordan,  "Natural-purification  of  Streams."  Paper  presented  at  the  :;6th 
annual  convention  of  the  American  Water  Works  Assn. 

t  See  Whipple,  "The  Microscopy  of  Drinking  Water,"  John  Wiley  &  Sons, 
1914. 


48  AIR,   WATER,  AND   FOOD 

ceedingly  disagreeable  and  may  render  a  water  supply  unfit  to 
deliver.  The  growths  can  generally  be  exterminated  by  the 
proper  use  of  copper  sulphate  in  quantities  which  will  kill  the 
small  organisms  but  are  not  injurious  to  the  human  system  (one 
part  to  from  one  to  20  million  parts  of  water). 

Surface  waters  often  have  color,  produced  usually  by  solu- 
tion, in  colloidal  form,  of  partly  decomposed  vegetable  matter, 
which  is  perfectly  harmless,  and  such  waters  should  not  be  con- 
demned unless  sewage  is  also  present.  They  are,  however,  often 
decolorized,  before  delivery,  by  means  of  alum.  Surface  waters 
are  generally  softer  than  ground  waters,  have  a  shght,  but  not 
disagreeable  odor,  may  be  more  or  less  turbid,  and  in  the  sum- 
mer time  are  Hable  to  be  warmer  than  is  desirable.  On  the 
whole,  however,  there  is  no  more  satisfactory  supply  for  a  large 
city  than  a  good  surface  water. 

Ground  Waters.  —  From  25  to  40  per  cent  of  the  annual  rain- 
fall in  temperate  regions  soaks  at  once  into  the  ground,  and 
passing  downward  through  the  soil  to  hardpan,  to  clayey  or 
impervious  layers,  or  to  rock  surface,  thence  through  crevices, 
broken  joints,  or  glacial  drift-deposits  to  the  water-table,  flows 
along  the  slope  for  many  miles  until  it  finds  its  way  again  to 
the  surface,  either  from  the  bottom  of  a  lake,  the  bed  of  a  river, 
the  side  of  a  hill,  supplpng  wells  or  appearing  as  springs.  In 
any  one  of  these  courses  it  may  be  intercepted  by  man  and 
caught  or  pumped  for  his  use.  Such  water  may  never  have 
been  far  from  the  surface;  it  may  have  been  used  and  returned 
to  the  ground  many  times;  it  may  have  appeared  as  surface- 
water  and  again  disappeared  to  great  depths.  It  has  been  esti- 
mated that  water  moves  in  the  ground  at  rates  varying  from 
0.2  to  20  feet  per  day.  This  movement  is  in  the  form  of  a  sheet, 
and  its  rapidity  as  well  as  the  amount  of  water  held  in  the 
ground  will  depend  on  the  geological  formation.  Thus  a  clay 
will  hold  more  water  than  loam  or  sand,  while  the  permeabihty 
is  just  the  reverse,  clay  being  nearly  impermeable.  Water  also 
passes  through  channels  in  rocks,  either  made  by  the  water  it- 
self or  consisting  of  cracks  and  fissures.     These  latter  are  often 


WATER  49 

a  source  of  danger,  as  no  purification  can  take  place  if  a  pol- 
luted water  travels  in  this  manner. 

This  long  contact  with  rocks  will,  of  course,  bring  mineral 
substances  into  solution  which  may  be  precipitated  as  new 
rocks  are  reached  or  other  streams  encountered,  so  that  the 
same  gallon  of  water  may  have  had  many  stages  in  its  course, 
and  may  have  held  many  different  substances  in  solution.  It  is 
no  wonder  that  so  active  a  solvent  as  water  should  take  with  it 
much  substance  whenever  it  remains  long  in  contact  with  soil 
or  rock,  for  it  may  be  months  before  that  which  has  once  sunk 
out  of  sight  again  appears.  In  fact,  great  rivers  are  supposed  to 
flow  into  the  sea  from  under  the  surface.  Tljjen,  too,  the  acquisi- 
tion of  dissolved  gases  favors  the  so^ation  of  many  substances; 
for  instance,  water  carrying  carbour  dioxide  dissolves  limestone. 

From  a  chemical  standpoint  ground  waters  may  be  divided 
into  two  classes,  —  (i)  springs  and  shallow  wells  (those  30  feet 
or  less  in  depth)  and  (2)  deep  and  artesian  wells.  In  general 
springs  and  shallow  wells  yield  softer  water  than  deep  wells  of 
the  same  region,  but  they  are  much  more  subject  to  pollution 
than  the  latter,  which,  if  built  so  as  to  exclude  any  surface 
water,  are  usually  a  safe  source  of  supply.  Pollution  does 
sometimes  enter  a  deep  well,  due  to  the  passage  of  water 
through  fissures  and  crevices  in  the  rocks. 

The  greatest  source  of  danger  is  the  shallow  well.  This  should 
never  be  used  in  a  thickly  populated  region,  and  in  country 
districts  only  when  it  can  be  placed  in  such  a  position  that  there 
can  be  no  connection  through  the  ground  with  a  privy  or  cess- 
pool. A  well  should  be  built  in  such  a  manner  that  no  surface 
water  can  enter  it,  and  the  walls  should  be  tight  to  a  depth  of 
five  to  10  feet  below  the  surface  in  order  that  any  water  which 
sinks  into  the  ground  may  be  sufficiently  filtered  before  enter- 
ing the  well.  The  area  from  which  a  well  ma}'  draw  varies 
with  the  permeability  of  the  soil,  and  may  have  a  diameter  of 
20  or  more  times  the  depth  of  the  well.  The  ground  which  is 
influenced  by  a  well  is  in  the  form  of  an  inverted  cone  whose 
apex  is  at  the  bottom  of  the  well. 


t- 


50  AIR,  WATER,  AND   FOOD 

If  a  well  is  found  upon  examination  to  be  polluted  with  sew- 
age it  is  often  desirable  to  find  the  source  of  trouble  in  order 
to  stop  further  pollution.  There  are  several  methods  of  doing 
this.*  A  survey  of  the  ground  and  the  conditions  surrounding 
the  well  is  often  sufficient  to  indicate  the  probable  sources,  but 
more  definite  evidence  may  be  required.  Some  substance  is 
then  added  to  the  suspected  source,  washed  into  the  ground 
with  a  large  amount  of  water,  and  the  well  examined  for  the  ap- 
pearance of  the  substance.  For  this  purpose  bacteria,  such  as 
B.  prodigiosus  and  B.  violaceous,  can  be  used.  These  organisms 
are  easily  grown,  are  harmless  and  can  readily  be  identified. 
If  these  do  not  reach  the  well  from  the  suspected  source  of 
pollution  it  is  fair  to  assume  that  no  pathogenic  organisms 
will  do  so,  but  will  be  filtered  out  in  passing  through  the 
ground.  The  only  uncertainty  with  this  method  is  that  while 
the  bacteria  may  be  sufficiently  removed  at  the  time  of  the  test, 
the  filter  may  sometime  break  down  and  allow  sewage  organ- 
isms, and  possibly  disease  germs,  to  enter  the  well.  It  is,  there- 
fore, better  not  to  use  a  well  water  which  receives  sewage  from 
any  nearby  source,  even  though  bacteria  are  being  eliminated 
in  passing  through  the  ground. 

Other  methods  of  tracing  the  source  of  pollution  are  by  the 
use  of  common  salt,  easily  tested  in  the  well  water  by  an  analysis 
for  chloride;  lithium  or  strontium  salts,  recognized  even  in 
minute  amounts  by  means  of  the  spectroscope;  and  fluorescent 
dyes  such  as  fluorescein,  which  are  readily  observed  in  a  glass 
of  water. 

One  method  of  obtaining  ground  water  in  comparatively 
large  quantities  is  by  means  of  the  so-called  "filter  gallery." 
This  consists  of  a  series  of  wells  dug  near  the  banks  of  a  river. 
It  was  originally  thought  that  a  suction  would  be  created  so  as 
to  draw  water  from  the  river  into  the  wells  through  a  layer  of 
soil  sufficient  to  remove  harmful  bacteria.  As  a  matter  of  fact, 
the  filter  gallery  actually  operates  by  intercepting  ground  water 

*  See  Thresh,  "Examination  of  Waters  and  Water  Supplies,"  2nd  edition,  pp. 

25-34- 


WATER  51 

on  its  way  to  the  river,  really  a  better  method  than  had  been 
intended.  In  sparsely  populated  regions  where  the  ground 
water  is  unpolluted,  good  results  have  been  and  are  being  ob- 
tained by  the  filter-gallery,  but  when  a  region  becomes  thickly 
settled  considerable  danger  results.  Furthermore,  in  times  of 
drought  water  may  be  drawn  from  the  river  bed,  and  if  this 
reaches  the  gallery  improperly  filtered,  a  typhoid  epidemic 
may  result.* 

In  general,  good  ground  waters  contain  more  mineral  matter 
than  surface  waters,  have  no  color  or  odor,  can  be  delivered  at 
a  lower  temperature,  and  are  often  more  palatable  than  surface 
waters.  It  is,  however,  more  difficult  to  obtain  large  supplies 
from  the  ground,  and,  therefore,  only  comparatively  small  com- 
munities can  avail  themselves  of  such  sources. 

Water  Purification.  —  Water  in  passing  through  the  ground 
may  undergo  a  number  of  changes  in  its  dissolved  and  suspended 
constituents.  If  this  water  contains  sewage  it  will  carry,  with 
other  suspended  matter,  a  large  number  of  bacteria,  some  of 
which  may  be  of  pathogenic  varieties.  If  the  polluted  water 
passes  through  not  too  coarse  soil,  the  bacteria  will  be  held  by 
the  soil,  and  thus  dangerous  disease  germs  will  probably  be  re- 
moved. Even  if  all  the  sewage  bacteria  are  not  removed  there 
will  still  be  some  protection  against  disease,  because  disease 
organisms  have,  in  general,  less  vitality  to  withstand  unfavor- 
able conditions  as  well  as  being  present  in  smaller  numbers  than 
less  harmful  varieties.  However,  there  is  still  some  chance  of 
these  bacteria  being  present  at  times,  and  it  is,  therefore,  not 
advisable  to  use  water  in  which  sewage  organisms  are  present. 

In  streams,  as  has  already  been  noted,  pathogenic  bacteria 
gradually  settle  to  the  bottom  and  die  out. 

Thus  there  is  some  natural  protection  against  the  spread  of 
disease  by  means  of  drinking  water,  but  it  is  not  safe  to  depend 
on  such  protection,  particularly  where  the  health  of  a  com- 
munity of  people  is  involved.     If  a  water  suppl}'  which  is  sub- 

*  See  "Typhoid  Fever  in  Des  Moines,  Iowa,"  /.  Am.  Med.  Assn.,  191 1,  56, 
p.  41. 


52  AIR,   WATER,   AND   FOOD 

ject  to  either  continuous  or  intermittent  pollution  has  to  be 
used,  some  method  of  artificial  purification  is  required  before  it 
can  be  safely  used  for  drinking  purposes.* 

There  are  two  general  methods  of  filtering  water  on  a  large 
scale.  The  first  is  known  as  slow  sand  filtration.  In  this 
method  the  water  is  run  through  a  layer  of  sand  from  two  to 
four  feet  thick,  supported  by  gravel  and  properly  underdrained. 
The  filter  beds  are  generally  built  in  units  of  one  acre  each,  and 
may  be  covered  or  not  depending  on  the  climatic  conditions. 
Previous  to  filtration  the  water  may  be  screened  and  stored  in 
reservoirs  to  allow  some  removal  of  suspended  matter,  includ- 
ing bacteria.  As  the  water  passes  through  the  sand  a  layer  of 
slimy  material  gradually  collects  on  the  surface,  which  acts  as 
the  real  straining  medium  and  holds  the  bacteria.  As  this 
material  collects  the  rate  of  filtration  decreases  until  a  point  is 
reached  where  it  is  uneconomical  to  continue.  The  water  is 
then  allowed  to  drain  out  from  the  sand,  the  top  layer  scraped 
off,  and  the  filter  again  started.  The  sand  removed  is  washed 
and  returned  to  the  filter  about  once  a  year.  A  slow  sand  filter 
operates  at  rates  of  from  one  and  a  half  to  three  million  gallons 
per  acre  per  day,  and  is  probably  the  most  efficient  method  of 
removing  bacteria  on  a  large  scale.  It  does  not,  however,  com- 
pletely remove  color  or  odor. 

The  other  method  is  that  known  as  rapid  filtration  (also,  un- 
fortunately, termed  mechanical  filtration).  Instead  of  allowing 
the  filtering  layer  to  form  from  the  matter  in  the  water  as  in 
slow  sand  filtration,  a  coagulant,  generally  alum,  is  added  to 
the  water.  The  alkali,  originally  present,  or  added,  precipi- 
tates aluminum  hydroxide  which  coagulates  the  suspended  par- 
ticles and  removes  the  color.  Part  of  the  hydroxide  is  allowed 
to  settle  out  and  the  remainder  is  put  on  a  filter  built  of  sand, 
where  it  collects  on  the  surface  and  forms  the  filtering  medium. 
The  filters  are  washed  about  every  eight  hours  by  reversing  the 
flow  of  water  and  agitating  the  sand  by  means  of  rakes  or  com- 
pressed air.     Filtration  takes  place  much  more  rapidly  by  this 

*  See  Hazen,  "The  Filtration  of  Public  Water  Supplies." 


WATER  53 

method,  being  at  rates  from  loo  to  150  million  gallons  per  acre 
per  day.  If  there  is  insufficient  alkali  present  naturally  in  the 
water  enough  must  be  added,  usually  either  as  sodium  carbon- 
ate or  as  calcium  carbonate,  to  completely  precipitate  the  alum 
and  leave  some  alkali  in  excess.  Alum,  being  acid,  if  allowed 
to  remain  in  the  water  renders  it  corrosive.  The  amounts  of 
alum  used  vary  from  one-tenth  to  three  grains  per  gallon  of 
water. 

Rapid  filtration  does  not  give  quite  as  high  a  bacterial  removal 
as  slow  filtration,  but  it  is  much  more  efficient  in  removing 
turbidity  and  particularly  color.  It  requires  a  smaller  invest- 
ment and  occupies  less  ground  for  the  same  amount  of  water 
filtered.  With  either  method  expert  control  is  necessary  in 
order  to  obtain  satisfactory  results. 

A  number  of  filters  on  the  same  principle  as  just  described, 
but  built  in  small  units,  are  on  the  market,  intended  to  supply 
hotels,  manufacturing  establishments,  swimming  pools,  etc. 
Many  of  them  give  reasonably  good  results  when  properly 
operated,  but  they  never  should  be  considered  to  be  automatic 
in  character.     They  all  need  careful  attention. 

Filters  still  smaller  are  sold  for  office  and  household  uses. 
These  generally  consist  of  artificial  stone  or  porcelain  through 
which  the  water  is  forced,  such  as  the  Pasteur-Chamberlain  or 
the  Berkefeld  filter.  If  the  stone,  or  candle  as  it  is  called,  is  in 
good  condition,  sterile  water  may  be  drawn  when  the  filter  is 
first  put  into  use,  but  the  bacteria  lodging  in  the  stone  grad- 
ually develop  and  may  grow  through  the  filter  so  that  as  water 
passes  through  it  will  wash  bacteria  with  it.  It  must  be  ad- 
mitted that  the  chances  are  that  pathogenic  organisms  will  not 
get  through.  If,  however,  there  is  a  crack  in  the  candle,  often 
too  small  a  one  to  be  visible,  the  filter  will  allow  all  kinds  of 
bacteria  to  pass.  One  of  the  great  objections  to  the  use  of  such 
filters  is  the  false  feeling  of  safet}'  which  they  may  inspire  in 
the  owners.  The  all  too  common  small  "filter"  which  screws 
on  the  faucet  is  not  only  useless,  but  worse. 

If  unsafe  drinking  water  must  be  used  in  a  house,  the  onlv 


54  AIR,  WATER,   AND   FOOD 

sure  method  is  to  bring  the  water  to  a  boil.  This  is  sufficient  to 
kill  any  harmful  intestinal  organisms.  Small  stills  which  can 
be  placed  on  the  back  of  the  stove  are  of  service  in  this  con- 
nection. The  fiat  taste  of  boiled  water  may  be  removed  by  the 
addition  of  a  pinch  of  salt  or  by  aeration. 

Sterilization  of  Water.  —  Where  a  badly  polluted  supply  is 
used,  or  extreme  caution  is  desirable,  or  where  a  good  supply 
suddenly  becomes  polluted  and  emergency  measures  deemed 
wise,  disinfection  may  be  resorted  to.  The  most  practical 
method  is  by  the  use  of  compounds  of  chlorine,  —  hypochlorite 
of  lime  (chloride  of  lime  or  bleaching  powder),  sodium  hypo- 
chlorite (electrolytic  bleach),  or  chlorine  gas  itself.  Of  these 
the  cheapest  under  ordinary  conditions  is  chloride  of  lime. 
This  has  the  disadvantage  of  being  disagreable  to  handle,  and 
of  not  dissolving  completely  in  water.  Amounts  of  from  -^^  to 
^Q  grains  per  gallon  are  generally  sufficient.  Sodium  hypo- 
chlorite can  be  used  where  there  is  cheap  electricity,  as  it  is 
made  by  passing  a  current  through  a  solution  of  common  salt. 
The  use  of  chlorine  gas  is  a  recent  development  and  appears  to 
be  giving  satisfactory  results,  although  considerably  more  ex- 
pensive than  the  other  methods. 

None  of  these  substances,  in  the  quantities  used,  are  in  any 
way  harmful.  Where  large  doses  are  given  complaints  are 
sometimes  received  that  they  can  be  tasted  in  the  water,  but, 
even  if  true,  this  is  not  a  necessary  consequence  of  their  use. 
The  disinfecting  action  is  probably  due  to  the  chlorine  itself. 

Electrical  methods  of  sterilization  are  also  in  somewhat 
limited  use.  One  of  these  is  through  the  formation  of  ozone  by 
an  electrical  discharge  through  air,  and  treatment  of  the  water 
with  the  ozonized  air.  Ozone,  in  the  presence  of  water,  is  a 
reasonably  good  disinfectant,  but  its  cost  makes  it  prohibitive  in 
most  places,  and  its  application  to  the  water  presents  some 
engineering  difficulty.  The  largest  plant  working  is  probably 
that  at  St.  Petersburg.* 

A  more  recent  development  than  ozone  is  the  use  of  ultra- 

*  See  Tillmans-Taylor,  "Water  Purification  and  Sewage  Disposal." 


WATER  55 

violet  light,  as  obtained  by  the  quartz-mercury-vapor  lamp. 
Ultraviolet  light  is  a  good  disinfectant,  but  it  is  expensive  to 
produce  in  most  places,  and  there  are  difficulties  in  applying  it 
to  waters  of  all  characters.  The  rays  will  not  penetrate  a  turbid 
or  colored  water  to  any  extent,  and,  therefore,  preliminary  filtra- 
tion and  decolorization  is  often  necessary.  This,  of  course,  adds 
greatly  to  the  expense.  The  method  may,  however,  fmd  use  in 
the  future,  if  it  is  possible  to  produce  it  for  a  reasonable  amount. 
Ice.  —  Questions  are  often  asked  concerning  the  use  of  ice 
in  drinking  water.  In  general,  natural  ice,  particularly  when 
stored  from  four  to  eight  months,  is  comparatively  safe.  In 
freezing,  suspended  and  dissolved  matter  is  not  removed  from 
the  water  with  the  ice,  except  a  small  amount  mechanically 
enclosed.  Furthermore,  it  has  been  shown  that  over  90  per 
cent  of  sewage  bacteria  die  out  on  storage.  Artiticial  ice,  if 
made  from  polluted  water,  is  not  safe,  as  in  the  method  used  all 
suspended  matter  is  frozen  into  the  center  of  the  cake.  If  the 
artificial  ice  is  made  from  unpolluted  or  from  distilled  water 
as  it  should  be,  it  is,  of  course,  perfectly  safe  to  use  for  all 
purposes. 


CHAPTER  V 

SAFE  WATER  AND  THE  INTERPRETATION  OF  ANALYSES 

Pure  water,  such  as  may  be  found  in  the  laboratory,  is  neither 
necessary  nor  probably  desirable  for  drinking.  There  are,  how- 
ever, certain  requirements  which  should  be  borne  in  mind  in 
looking  for  a  supply.  First,  the  water  should  be  free  from  sew- 
age and  all  other  waste  products.  Second,  it  should  not  con- 
tain an  excessive  amount  of  mineral  matter.  Third,  it  should 
be  free  from  color,  odor,  taste  and  suspended  matter,  and 
should  be  delivered  at  a  temperature  not  over  15°  C.  It  is 
obvious  that  all  of  these  requirements  cannot  always  be  lived 
up  to,  but  it  is  essential  that  the  first  one  should  be,  even  at  the 
expense  of  the  other  two.  A  water  free  from  sewage  and  other 
waste  products  can  be  called  a  ''safe"  water.  Unfortunately, 
physical  appearance  is  taken  as  the  criterion  of  the  safety  of  a 
supply  by  too  many  people.  The  cool,  clear,  colorless  water  is 
much  to  be  preferred  to  the  safe  colored  or  muddy  one;  and  it 
is  sometimes  difficult  to  persuade  the  user  of  such  a  supply  as 
the  former  that  he  may  be  endangering  his  health  by  drink- 
ing it  when  tests  have  shown  the  presence  of  sewage.  Since 
appearance  is  of  such  importance,  it  is  necessary  to  take  this 
into  account  in  any  water  examination. 

Since,  as  already  described,  a  water  once  in  contact  with 
sewage  may  become  purified  and  be  rendered  safe  for  drinking 
purposes,  and  since  water  is  so  universally  made  a  carrier  of 
refuse  that  it  is  difficult  to  find  a  stream  or  well  which  has  nev^er 
been  at  any  time  in  contact  with  waste,  certain  arbitrary  stand- 
ards have  been  chosen  to  determine  when  a  water  may  be  called 
safe,  on  the  basis  of  an  analysis.  Such  limits  are  very  mislead- 
ing of  themselves,  especially  if  used  over  a  wide  extent  of  ter- 
ritory.    The  English  standards,  for  instance,  are  not  applicable 

56 


SAFE  WATER  57 

to  eastern  North  America.  Only  a  study  of  all  local  conditions 
and  a  wise  interpretation  of  all  results  can  make  standard 
figures  of  any  significance.  This  is  true,  also,  of  bacterial  re- 
sults in  surface  waters.  In  lakes  and  streams  there  are  so 
many  varieties  of  bacteria  present  and  in  such  varying  numbers, 
according  to  wind  and  rain  and  water-shed,  that  taken  alone 
the  numerical  count  gives  no  more  convincing  proof  than  is 
found  in  chemical  figures. 

While  it  is  quite  within  the  limits  of  possibility  that  a  cul- 
ture-tube of  typhoid  bacilU  might  be  emptied  into  the  middle 
of  a  river  or  be  washed  into  a  reservoir,  and  chemical  analysis 
give  no  sign,  yet  no  continuous  natural  means  of  contamination 
is  known  which  is  not  accompanied  by  substances  readily  de- 
tected by  suitable  chemical  examination. 

Sanitary  Examination.  —  The  examination  of  a  water  to  de- 
termine its  safety  for  domestic  use  is  called  a  sanitary  analysis, 
in  distinction  from  that  examination  which  determines  its  fit- 
ness for  manufacturing  purposes,  for  use  in  steam  boilers,  or  its 
medicinal  value.  Such  an  examination  may  be  either  bacterio- 
logical or  chemical  in  character,  but  the  object  in  either  case  is 
the  same,  that  is,  to  determine  the  absence  of  sewage  or  its 
presence  in  quantities  sufl'icient  to  render  the  water  dangerous 
to  drink.  In  neither  kind  of  examination  are  the  harmful  sub- 
stances themselves  sought  for.  Typhoid  organisms  have  been 
isolated  from  water  during  epidemics  in  only  a  few  cases  and 
the  process  is  a  long  and  tedious  one.  Furthermore,  such  a 
search  would  often  be  useless  for  an  infected  person  does  not 
usually  come  down  with  the  disease  until  lo  to  14  days  after 
infection,  and  the  organisms  might  have  died  during  this  time. 
Also,  one  does  not  care  to  wait  until  an  epidemic  starts  before 
examining  the  water  supply,  but  desires  to  know  in  advance 
whether  or  not  there  is  any  possibility  of  trouble.  The  presence 
or  absence  of  sewage  determines  this  possibility. 

In  a  bacteriological  examination,  the  presence  of  sewag.c  is 
determined  first,  by  counting  the  total  number  of  bacteria  per 
cubic  centimeter,  and  second,  by  looking  for  some  type  of  dis- 


S8  AIR,   WATER,   AND   FOOD 

tinctly  sewage  organism,  such  as  B.  coli.  The  total  count  has 
little  signilicance  in  a  surface  water,  but  in  a  well  or  filtered 
water,  should  not  be  over  loo  bacteria  per  cubic  centimeter. 
B.  coli  should  not  be  present  in  numbers  of  one  or  more  per 
cubic  centimeter.  Considerable  discussion  surrounds  the  de- 
termination of  this  organism,  but  it  is  quite  impossible  to  see 
what  difference  it  makes  whether  the  bacteria  isolated  show  all 
the  typical  reactions  of  B.  coli  communis  or  not.  The  members 
of  the  colon  group  get  into  a  water  supply  practically  only  with 
sewage,  and  it  should  not  make  any  difference  in  the  interpre- 
tation of  results,  as  to  what  particular  member  of  that  group  is 
found.  For  the  methods  of  making  these  determinations  the 
reader  is  referred  to  some  book  on  bacteriology.* 

Before  proceeding  with  the  laboratory  test  of  a  water,  it  is 
essential  to  know  something  of  the  surroundings  of  the  source 
of  supply.  So  long  as  the  eye  can  re-enforce  the  other  tests  and 
the  whole  course  of  the  water  may  be  clearly  traced,  it  is  com- 
paratively easy  to  judge  of  the  character  of  a  supply  and  of  its 
safety  for  human  use;  but  when  a  hole  in  the  ground  is  the 
visible  source,  or  the  actual  history  of  the  water  is  hidden  in 
unknown  distances  and  depths,  the  diagnosis  is  more  difficult. 

The  geological  horizon  and  superficial  soil  must  be  studied; 
the  direction  and  flow  of  underground  water,  not  the  slope  of  the 
surface  only;  the  possible  sources  of  danger,  occasional  as  well 
as  constant,  within  at  least  a  quarter  of  a  mile  radius.  The 
composition  of  unpolluted  water  of  the  same  region  should 
always  be  at  hand  for  consultation. 

An  examination  of  the  environment  is  often  sufficient  to  con- 
demn a  water,  but  cannot  usually  give  it  a  clear  certificate. 
Laboratory  tests  should  follow.  In  the  next  paragraphs  will 
be  found  a  discussion  of  the  interpretation  of  sanitary  chemical 
analyses. 

Expression  of  Results.  —  Results  of  a  sanitary  chemical 
analysis  should  be  expressed  in  parts  of  any  particular  substance 

*  Prescott  and  Winslow,  "  Elements  of  Water  Bacteriology."  John  Wiley  & 
Sons,  New  York,  1913. 


SAFE   WATER  59 

per  million  of  water.  In  most  cases  this  is  equivalent  to  milli- 
grams per  liter  —  the  exceptions  being  where  the  water  has  an 
appreciable  specific  gravity  above  i.o,  such  as  sea  water. 

Accuracy  of  Methods.  —  In  all  water  analyses  very  minute 
quantities  are  sought  after,  and,  therefore,  all  the  tests  applied 
must  be  exceedingly  delicate  in  character.  The  quantitative 
results  need  not,  however,  be  of  great  percentage  accuracy. 
For  example,  it  makes  no  particular  difference  whether  0.050 
or  0.055  parts  of  ammonia  per  million  of  water  are  found  —  an 
error  of  10  per  cent.  It  might  make  a  good  deal  of  difference 
if  one  found  0.2  of  a  part  or  0.05  —  a  difference  of  0.15  parts 
per  million,  an  amount  which  in  most  analytical  work  would  be 
entirely  negligible.  The  American  Public  Health  Association 
has  suggested  that  only  a  limited  number  of  figures  be  used  in 
reporting  an  analysis,  and  thereby  eliminate  any  impression  of 
false  accuracy. 

Above  10  parts  per  million.  Use  no  decimals. 

From  I  to  10  parts  per  million.   Use  i  decimal. 
From  0.1  to  I  part  per  million.   Use  2  decimals. 

In  the  determinations  of  ammonia  and  of  nitrites  3  decimals 
may  be  used. 

The  above  discussion  does  not  mean  that  the  analyses  should 
be  made  in  a  careless  or  slipshod  manner,  in  fact,  quite  the  re- 
verse is  true,  for  there  is  no  kind  of  chemical  work  which  requires 
greater  care  or  cleanliness. 

As  little  time  as  possible  should  elapse  between  the  collection 
and  examination  of  samples  of  water.  The  more  polluted  the 
water  the  more  rapidly  will  changes  take  place,  and,  therefore, 
all  samples  should  be  tested  within  24  hours  of  their  collection. 
Samples  for  bacterial  analysis  should  be  examined  immediately, 
or  if  sent  to  a  laboratory,  should  be  packed  in  ice.  Sewages  and 
sewage  effluents  should  be  analysed  within  six  hours  of  collec- 
tion, or  if  for  chemical  analysis  should  be  chlorofonned  (5  c.c. 
per  liter)  to  prevent  chemical  changes  taking  place. 

Chemical  Examinations.  —  The  chemical  analyses  generally 
made  in  sanitary  work  are  the  following:    nitrogen  as  free  am- 


6o  AIR,  WATER,  AND   FOOD 

monia,  as  albuminoid  ammonia,  as  nitrates,  and  as  nitrites; 
chlorides  in  terms  of  chlorine;  oxygen  consumed;  soap  hard- 
ness; total  solids  and  loss  on  ignition;  iron;  and  sometimes 
oxygen  dissolved.  The  interpretation  of  the  results  of  each  of 
these  will  be  discussed,  and  where  possible,  standard  figures  will 
be  given. 

Nitrogen  Cycle.  —  The  most  important  determinations  which 
must  be  made  in  order  to  decide  on  the  potability  of  the  water 
in  question  are  those  involving  the  nitrogen  compounds  and 
chlorides.  A  clear  understanding  of  the  cycle  of  nitrogen  in 
nature  is,  therefore,  necessary. 

Nitrogen  is  present  in  living  plants  and  animals  mainly  in 
the  form  of  organic  compounds  —  the  proteins  and  simpler 
amino  compounds.  These  substances,  if  boiled  with  alkaline 
potassium  permanganate,  will  give  off  part  of  the  nitrogen  in 
the  form  of  ammonia  which  can  be  collected  and  determined 
quantitatively.  This  is  called  "albuminoid  ammonia."  When 
the  living  plant  or  animal  dies,  the  proteins  are  attacked  by 
bacteria  and  putrefy.  In  this  process  the  nitrogen  is  converted 
first  into  simpler  amino  bodies  and  finally  into  ammonium  salts 
or  substances,  such  as  urea,  which  readily  yield  ammonia.  Thus, 
the  detemiinations  of  ammonia  (called  "free"  ammonia)  and 
of  albuminoid  ammonia  will  indicate  how  far  this  putrefaction 
has  gone.  A  waste  product,  such  as  sewage,  will  give,  when 
fresh,  both  free  and  albuminoid  ammonia  in  quantity,  but  on 
standing,  some  of  the  organic  nitrogen  will  change  to  ammonia, 
so  that  the  free  ammonia  will  increase  and  the  albuminoid  am- 
monia decrease.  Thus,  these  analyses  may  be  used  to  indicate 
fresh  or  recent  sewage  pollution  of  a  water  supply. 

When  the  organic  nitrogen  is  largely  converted  to  ammonium 
compounds,  and  if  oxygen  is  present,  another  kind  of  bacteria, 
called  the  nitrosomonas,  will  act  on  the  latter  substances  and 
oxidize  them  to  nitrites.  This  is  the  second  stage  in  the  nitrogen 
cycle.  Thus,  the  presence  of  nitrites  in  a  water  may  indicate 
less  recent  pollution  than  the  presence  of  only  free  ammonia. 

The  nitrites,  however,  are  not  stable,  and  if  sufficient  oxygen 


SAFE  watp:r  6 1 

is  available,  they  are  oxidized  by  still  another  set  of  micro- 
organisms, the  nitrobacter,  giving  nitrates.  The  nitrifying  bac- 
teria remained  undiscovered  for  some  time,  owing  to  the  fact 
that  they  do  not  grow  in  the  laboratory  on  any  medium  con- 
taining large  amounts  of  organic  matter.  Thus,  the  presence  of 
nitrates  in  a  drinking  water  may  indicate  contact  with  sewage 
at  some  past  time,  or  as  it  is  called,  past  pollution. 

Nitrates  are  food  for  green  plants,  which  in  turn  die  or  are 
eaten  by  animals,  the  nitrogen  being  changed  from  the  inor- 
ganic back  to  the  organic  form,  and  the  cycle  thus  completed. 

But  the  cycle  is  not  so  simple  as  would  appear.  Nitrogen 
may  be  lost  from  it  in  two  w^ays.  While  ammonia  is  being  oxi- 
dized to  nitrites,  both  may  be  present  and  interaction  may 
result  with  the  formation  of  nitrogen  gas. 

NH3  +  HNO2  -^  No  4-  2  H2O. 

Or,  nitrites  may  be  reduced  by  micro-organisms  with  the  liber- 
ation of  nitrogen.  Nitrates  may  also  be  reduced  to  nitrites  by 
bacteria,  iron,  or  possibly  by  organic  matter. 

Nitrogen  may  be  added  to  the  cycle  as  well  as  lost  from  it. 
This  takes  place  by  means  of  the  nitrogen-fixing  bacteria  which 
occur  largely  in  nodules  on  the  roots  of  leguminous  plants,  such 
as  the  clover,  and  also  in  some  soils.  These  have  the  power  of 
removing  nitrogen  from  the  air  and  making  it  available  for  the 
plant. 

Practical  use  is  made  in  the  septic  or  Imhoff  tanks  of  the 
ability  of  micro-organisms  to  decompose  organic  matter  and  the 
modern  sewage  filter  is  really  a  culture  bed  for  the  development 
of  nitrifying  organisms  w^hich  act  on  the  sewage  and  render  it 
stable  by  oxidizing  the  nitrogen  compounds  to  nitrates. 

As  will  be  seen  from  the  above  discussion,  a  sanitary  chemical 
analysis  depends  primarily  upon  the  determination  of  the  con- 
dition of  the  nitrogen  compounds  in  a  sample  of  water.  Each 
of  these  will  be  discussed  separately. 

Albuminoid  Ammonia.  —  This  is  the  ammonia  which  is  set 
free  by  the  action  of  boiling  alkaline  potassium  permanganate 


62  AIR,  WATER,  AND   FOOD 

on  nitrogenous  organic  matter.  This  may  have  entered  the 
water  from  perfectly  harmless  sources,  such  as  dead  vegetable 
substances,  or  it  may  have  come  from  waste  material,  such  as 
sewage.  If  from  the  former  source,  it  is  relatively  stable  and,  if 
present  in  any  quantity,  is  accompanied  by  color  in  the  water. 
If  from  sewage,  there  may  be  little  or  no  color,  and  the  nitrog- 
enous matter  will  be  relatively  unstable.  The  stability  can  be 
determined  by  the  action  of  the  permanganate,  stable  substances 
yielding  ammonia  only  slowly  and  unstable  substances  losing  it 
rapidly. 

The  albuminoid  ammonia  gives  no  accurate  measure  of  the 
total  nitrogenous  organic  matter  present,  as  only  about  50  per 
cent  is  converted  to  ammonia,  but  it  does  give  a  good  indica- 
tion of  whether  or  not  the  organic  matter  is  easily  decomposed, 
and,  therefore,  whether  or  not  it  comes  from  sewage.  A  color- 
less water  should  not  contain  over  0.15  parts  per  million  of 
nitrogen  as  albuminoid  ammonia.  The  amounts  found  in  good 
ground  waters  are  generally  much  lower  than  this  figure. 
Samples  from  storage  reservoirs,  in  which  there  is  plant  life,  may 
contain  larger  amounts  —  up  to  0.4  of  a  part. 

The  total  organic  nitrogen  as  determined  by  the  Kjeldahl 
method  is  sometimes  used  in  place  of  the  albuminoid  ammonia, 
but  it  gives  no  means  of  distinguishing  between  stable  and  un- 
stable substances,  and  is  not  considered  in  this  country  to  be  as 
good  an  index  of  pollution. 

Free  Ammonia.  —  This  is  the  ammonia  which  comes  off  from 
a  water  on  direct  distillation,  the  water  being  made  alkaline  if 
necessary.  The  ammonia  is  probably  present  as  ammonium 
salts.  Since  this  represents  the  first  stage  in  the  decomposition 
of  unstable  nitrogenous  organic  matter,  its  presence  in  abnormal 
quantities  may  be  taken  as  an  index  of  sewage  pollution.  The 
amounts  of  ammonia  present  in  good  waters  are  generally  very 
small,  and  amounts  over  0.15  to  0.2  parts  expressed  in  terms  of 
nitrogen  are  sufficient  to  indicate  pollution.  In  general,  the  free 
ammonia  is  less  than  the  albuminoid  ammonia.  If  the  reverse 
is  found  it  is  an  indication  of  trouble,  unless  both  are  very  low. 


SAFE   WATER      '  63 

Cases  sometimes  arise  where  abnormally  high  free  ammonia 
does  not  indicate  sewage,  and  the  analyst  should  continually  be 
on  the  lookout  for  these  exceptions.  One  may  be  found  in  wells 
dug  in  glacial  drift,  where  ammonia  may  have  come  from  fossil 
remains.  Another  occurs  sometimes  when  a  well  is  located  in 
close  proximity  to  an  ammonia  refrigerating  plant. 

Nitrites.  —  Nitrites  in  a  water  are  formed  either  from  the  oxi- 
dation of  ammonia  or  the  reduction  of  nitrates.  In  either  case, 
they  represent  an  unstable  condition,  usually  accompanied  by 
large  numbers  of  bacteria,  and  in  most  cases  sewage  pollution 
or  surface  contamination.  As  has  been  said,  "a  state  of  change 
is  a  state  of  danger,"  and  the  presence  of  nitrites  reveals  this 
condition.  As  has  been  mentioned,  nitrites  may  be  formed 
from  nitrates  by  reduction  due  to  iron  or  organic  matter,  but 
such  cases  are  not  at  all  usual. 

A  good  drinking  water  should  be  either  entirely  free  from 
nitrites  or  should  contain  them  only  in  very  minute  quantities. 
Amounts  of  o.oi  to  0.02  or  more  parts  per  million  of  nitrogen 
are  sufficient  to  condemn  a  water.  But  while  the  presence  of 
abnormal  amounts  of  nitrites  indicates  danger,  their  absence  is 
no  guarantee  of  the  purity  of  a  supply. 

Nitrates.  —  As  seen  from  the  discussion  of  the  nitrogen  cycle, 
nitrates  are  the  fmal  stage  in  the  oxidation  of  nitrogen  com- 
pounds. Since  they  are  food  for  plants,  we  would  expect  to 
find  only  small  amounts  where  there  is  any  plant  life.  Thus, 
surface  waters  are  generally  low  in  nitrates  while  ground  waters 
may  be  higher.  It  is  probable  that  practically  all  nitrates  in 
waters  have  come  originally  from  animal  matter,  as  vegetable 
nitrogen  is  not  easily  oxidized.  In  some  cases,  nitrates  have 
been  known  to  come  from  chemical  fertilizers  used  on  fields. 

High  nitrates,  combined  with  high  chlorides,  indicate  past 
pollution.  "Past"  is  used  either  in  the  sense  of  time  or  dis- 
tance. That  is,  fresh  sewage  may  have  found  its  way  into  a 
well  at  some  time  past,  and  the  nitrogen  compounds  may  ha\-e 
remained  there,  and  1)ccn  oxidized  until,  at  the  time  of  examina- 
tion, nitrates  predominated  over  the  other  fomis.     Or  the  sew- 


64  AIR,  WATER,  AND   FOOD 

age  may  have  come  from  such  a  distance  that  oxidation  has 
taken  place  in  the  passage  through  the  ground. 

The  presence  of  high  nitrates  is  not  generally  accompanied 
by  sewage  bacteria,  and,  therefore,  immediate  danger  from  the 
supply  does  not  exist.  The  objection  to  using  such  waters  for 
drinking  is,  first,  that  if  pollution  has  once  entered,  it  may  enter 
again,  and,  second,  that  the  natural  filter  through  which  the 
water  is  passing  may,  at  some  time,  fail  to  work  properly  and 
allow  sewage  bacteria,  and  with  them  possibly  typhoid  organ- 
isms, to  enter  the  water.  In  other  words,  past  pollution  indi- 
cates a  condition  of  possible  future  danger,  and  it  is  safest  to 
avoid  this  either  by  not  drinking  such  water  or  by  watching  it 
carefully  by  means  of  frequent  examination. 

Good  surface  waters  are  low  in  nitrates,  over  i  part  of  nitrogen 
as  nitrate  per  million  of  water  being  a  suspicious  sign.  Ground 
waters  often  run  much  higher  than  this  even  when  unpolluted, 
but  above  5.0  parts,  is  in  most  cases,  sufhcient  to  condemn  the 
water  as  unsafe  for  drinking. 

Chlorides.  —  In  interpreting  the  results  of  the  analyses  of  the 
various  nitrogen  compounds,  it  must  be  remembered  that  the 
presence  of  any  one  of  them  in  abnormal  amounts  is  rarely 
sufficient  evidence  upon  which  to  declare  a  water  unfit  to  drink. 
The  nitrogen  compounds  must  be  accompanied  by  an  abnormal 
amount  of  chlorides.  Chlorides  occur  in  w^aters  principally  as 
the  sodium  salt,  and  as  the  results  of  analysis  are  generally  ex- 
pressed in  terms  of  chlorine,  this  latter  term  is  the  one  in  common 
use.  Human  urine  contains  about  i  per  cent  sodium  chloride, 
and  the  amount  of  sewage  entering  a  well  or  stream  can  be  ap- 
proximately determined  by  the  rise  in  the  chlorine  content. 
Furthermore,  chlorine  passes  through  no  such  cycle  as  that  of 
nitrogen,  and  common  salt  is  not  taken  up  by  most  plants,  so 
that  once  in  a  water  there  is  no  way  by  which  the  chlorine  can 
entirely  disappear.  If,  then,  abnormal  amounts  of  chlorine 
accompanied  by  abnormal  amounts  of  one  of  the  nitrogen  com- 
pounds are  found  in  a  water,  it  is  a  pretty  sure  indication  that 
sewage,  in  some  state,  is  entering. 


STATE  BOARD  OF  HEALTH 

MAP  OF  THE 

The  lilies  represent  normal  chlorine. 

STATE  OF  MASSACHUSETTS.  ^^SrortL.T"^  °'"°''°''  ""■* ' 

Q 'tf  r^WTT  TSif"*  "^^  flRureB  uoderlined  rwppesenicliJorlnea  of  ground- 

NORMAL  CHLORINE. 


SAFE   WATER  65 

The  difficulty  is  to  decide  on  what  constitutes  an  abnormal 
amount  of  chlorine,  since  salt  occurs,  to  some  extent,  in  most 
soils  and  rocks,  and  in  some  places  in  very  large  quantities. 
Some  years  ago,  the  Massachusetts  State  Board  of  Health  at- 
tempted to  solve  this  problem  by  a  careful  study  of  a  large 
number  of  waters  from  all  over  the  state.  The  chlorine  was 
determined  in  those  which,  from  the  surroundings  and  the  other 
constituents,  could  safely  be  regarded  as  free  from  pollution. 
The  figures  obtained  were  placed  on  a  map  of  the  state  at  the 
appropriate  places  and  lines  drawn  through  ecjual  values.  These 
lines  were  termed  "isochlors."  This  map  is  shown  opposite. 
(Note.  The  figures  are  given  on  the  map  in  parts  per  100,000.) 
Since  this  map  was  made  for  Massachusetts,  a  number  of  other 
states  have  made  similar  ones.  The  maps  give  with  reasonable 
accuracy  the  normal  chlorine  values  for  surface  waters,  but  for 
deep  or  artesian  wells,  the  figures  do  not  necessarily  hold.  Con- 
sequently, in  some  states,  for  example  in  Illinois,  it  has  been 
found  more  satisfactory  to  give  normal  values  according  to  the 
source  of  the  supply. 

But  the  presence  of  chlorine  in  amounts  above  normal,  alone, 
is  not  sufficient  to  condemn  a  water.  High  chlorine  and  low 
nitrogen  are  sometimes  found  together  in  a  well  water  which 
has  been  contaminated  with  wastes  from  a  sink  drain.  The 
ratio  of  nitrogen  to  chlorine  can  sometimes  be  used  to  distin- 
guish between  barn  and  human  sewage,  as  the  former  contains 
less  chlorine  than  the  latter  for  the  same  amount  of  nitrogen. 
Excessively  high  nitrates  with  chlorine  only  slightly  above 
the  normal  sometimes  indicates  washings  from  a  fertilized 
field. 

Mineral  Matter.  —  Since  water  is  a  universal  solvent,  it  is  not 
surprising  to  find  considerable  amounts  of  mineral  matter  under 
the  headings  "total  solids''  and  "hardness."  How  much  cal- 
cium sulphate  or  magnesium  chloride  or  other  soluble  mineral 
matter  is  allowable  in  a  potable  water  is  for  the  physician  rather 
than  the  chemist  to  say,  but  it  seems  to  be  the  consensus  of 
opinion  that,  for  the  normal  healthy  person,  the  presence  of 


66  AIR,  WATER,  AND   FOOD 

mineral  matter,  even  in  considerable  quantities,  is  in  no  way 
deleterious  to  the  system. 

As  has  been  said,  the  human  system  possesses  great  adapta- 
bility, not  only  for  different  foods,  but  for  mineral  substances 
water-carried.  Not  so  the  steam-boiler  or  the  laundry-tub, 
which  reacts  very  sensitively  and  affects  the  pockets  of  the 
consumers.  The  determination  of  sulphates  gives  an  indi- 
cation as  to  how  the  hardness  is  divided,  as  permanent  hard- 
ness is  caused  principally  by  calcium  sulphate. 

In  a  region  of  soft  water,  high  soUds  with  chlorine  and  nitrates 
indicate  sewage  pollution.  Silica  is  much  more  commonly 
present,  even  in  surface-waters,  than  is  often  supposed.  What 
its  effect  may  be  is  unknown.  Iron  is  not  uncommonly  found  in 
combination  with  organic  matter  in  either  surface  or  imperfectly 
filtered  waters  in  contact  with  soils  poor  in  calcium  salts.  It  is 
frequently  accompanied  by  free  ammonia,  which  causes  an 
abundant  growth  of  Crenothrix.  It  is  also  present  in  deep  wells 
in  the  form  of  bicarbonate,  which  precipitates  on  exposure  to 
warm  air. 

Organic  Matter.  —  The  amount  of  carbonaceous  matter,  de- 
termined either  by  the  oxygen-consumed  test  or  by  the  loss  on 
igniting  the  soHds,  is  of  little  use  in  interpreting  a  water  analysis; 
it  is  too  difficult  to  get  concordant  results.  The  latter  test  may 
sometimes  be  of  service  in  a  qualitative  way,  because  the  residue 
from  a  recently  polluted  water  often  gives  a  distinctive  disa- 
greeable odor  when  ignited.  In  some  laboratories,  the  quan- 
titative determination  is  omitted  entirely. 

Dissolved  Oxygen.  —  During  the  last  few  years,  the  determina- 
tion of  the  oxygen  dissolved  in  water  has  assumed  considerable 
importance,  because  of  the  use  of  the  test  as  an  indication  of 
the  sanitary  condition  of  a  harbor  or  river.  As  long  as  sufficient 
oxygen  is  present,  the  putrefactive  changes  which  give  off  dis- 
agreeable odors  will  not  take  place.  There  is  some  difference  of 
opinion  as  to  how  low  the  oxygen  content  may  be  allowed  to  fall 
and  still  prevent  these  changes,  but  40  per  cent  of  saturation  is 
a  safe  figure  to  use. 


SAFE  WATER  67 

The  test  is  also  used  to  determine  the  putrescibiHty  of  a 
sewage  effluent  as  described  later  under  that  test.  The  object 
is  to  determine  the  amount  of  oxygen  absorbed  by  the  organic 
matter  in  the  effluent. 

Physical  Tests.  —  These  are  of  little  importance  as  far  as  the 
determination  of  pollution  is  concerned,  but  are  generally  in- 
cluded in  an  examination  in  order  to  satisfy  those  who  insist 
that  a  water  shall  be  attractive  as  well  as  safe. 

Sewage  Analysis.  —  Sewages  may  be  tested  to  determine 
their  strength  and  constituents  in  order  to  help  in  deciding  upon 
the  best  method  of  treatment,  and  also  as  a  basis  for  determin- 
ing the  amount  of  purification  which  any  process  gives.  The 
analysis  of  effluents  is  carried  on  also  for  this  latter  purpose,  and 
in  order  to  determine  their  putrescibiHty.  For  an  extended 
discussion  the  reader  is  referred  to  another  book.* 

Value  of  Tests.  —  It  is  often  asked  if  some  tests  cannot  be 
made  by  the  ordinary  person  of  average  intelligence  which 
will  enable  him  to  tell  the  quality  of  a  water  as  well  as  the 
expert  to  whom  he  pays  ten  or  twenty  dollars  for  an  opinion. 
A  careful  perusal  of  the  preceding  pages  will  have  answered 
the  question  in  the  negative.  There  is  no  assay  of  water  as 
there  is  of  gold  and  silver.  Not  one,  but  ten  or  twenty  tests 
must  be  made.  Not  only  must  the  tests  be  made  with  the 
utmost  care  and  cleanliness  of  person,  utensils,  and  room,  but 
the  results  must  be  studied  in  the  light  of  other  experience  and 
other  knowledge,  geological  and  biological,  and  after  all  this  is 
done,  there  is  an  array  of  circumstantial  evidence  which  must 
be  carefully  weighed  by  one  whose  judgment  and  experience 
enable  him  to  read  clearly  where  another  might  see  nothing. 
The  value  of  a  water-analysis  is  in  direct  proportion  to  the 
knowledge  and  experience  of  the  one  who  interprets  it.  Clinical 
skill  in  addition  to  theoretical  knowledge  is  as  much  required 
to  interpret  the  figures  obtained  in  the  course  of  a  water-analy- 
sis, as  in  the  diagnosis  of  a  disease;  and  the  analog}^  goes  still 
further,  for  just  as  some  diseases  are  clearly  defined,  and  others 
*  Fowler,  ''  Sewage  Works  .\nalysis." 


68  AIR,   WATER,  AND   FOOD 

are  so  complicated  that  only  those  who  have  had  long  experience 
can  outline  a  safe  course  of  treatment,  so  some  waters  bear  the 
marks  of  their  character  so  plainly  as  not  to  admit  of  mistake, 
while  others  require  most  careful  study.  For  these  reasons,  the 
value  of  water-analysis  should  not  be  decried  because  the  fears 
aroused  by  reports  given  by  unskilled  analysts  prove  ground- 
less, any  more  than  the  practice  of  medicine  should  be  discarded 
because  inexperienced  men  make  mistakes. 

Is  the  water  in  any  given  case  safe  for  drinking?  To  answer 
this  question  there  is  needed  a  knowledge,  wider  than  a  chem- 
ist's, of  the  relation  of  decaying  organic  matter  and  of  the 
germ-carrying  power  of  water  to  outbreaks  of  disease.  There 
must  be  added  the  knowledge  of  the  biologist,  the  engineer, 
and  the  sanitarian. 


CHAPTER  VI 

WATER :  ANALYTICAL  METHODS  * 

Water-analysis  cannot  be  carried  on  in  an  ordinary  labora- 
tory. In  order  to  obtain  satisfactory  results,  it  is  necessary  to 
have  a  room  set  apart  for  the  purpose,  and  to  exclude  rigidly  all 
operations  which  tend  to  the  production  of  fumes  or  dust. 
Where  such  minute  traces  of  substances  are  dealt  with  as  in 
water-analysis,  too  much  care  cannot  be  taken  to  insure  the 
absolute  cleanliness  of  the  apparatus  and  the  surroundings.  It 
is  desirable  that  the  room  be  well  lighted,  and,  if  possible,  the 
windows  should  face  toward  the  north. 

For  the  collection  of  water  samples,  glass-stoppered  bottles  of 
about  a  gallon  capacity  are  best.  Those  used  in  this  laboratory 
are  of  white  glass,  15  inches  high  to  the  top  of  the  stopper,  five 
and  a  half  inches  in  diameter,  and  weigh  about  three  pounds. 
They  have  flat,  mushroom  stoppers,  on  each  of  which  is  engraved 
a  number  to  correspond  with  that  on  the  bottle.  The  bottles, 
before  being  sent  out,  are  thoroughly  cleaned  with  potassium 
bichromate  and  sulphuric  acid,  washed  with  distilled  w^ater  and 
dried.  If  glass-stoppered  bottles  are  not  at  hand,  new  demi- 
johns fitted  with  new  corks  may  be  used.  A  glass  bottle  or  a 
demijohn  is  much  to  be  preferred  to  an  earthenware  jug,  because, 
if  for  no  other  reason,  it  is  so  much  easier  to  be  sure  that  the 
interior  is  clean.  It  should  always  be  borne  in  mind  that  in 
water-analysis  the  question  is  one  of  very  minute  quantities  of 
material,  and  that  the  methods  to  be  employed  are  extremely 
deHcate.  Hence,  in  the  case  of  many  waters,  careless  handling 
of  the  sample  would  contaminate  the  water  to  a  sufficient  ex- 
tent to  render  valueless  the  results  obtained  in  the  laboratory. 

*  See  "  Standard  Methods  for  the  Examination  of  Water  and  Sewage,"  Ameri- 
can Public  Health  Association,  1912. 

69 


70  AIR,   WATER,   AND    FOOD 

In  collecting  samples,  the  following  directions  should  be  closely 
followed:* 

Directions  for  Collecting  Samples  for  Analysis.  —  From  a 
Water-tap.  —  Let  the  water  run  freely  from  the  tap  for  a  few 
minutes  before  collecting  the  sample.  Then  place  the  bottle 
directly  under  the  tap  and  rinse  it  out  with  the  water  three 
times,  pouring  out  the  water  completely  each  time.  Place  it 
again  under  the  tap;  fill  it  to  overflowing  and  pour  out  a  small 
quantity  so  that  there  shall  be  left  an  air-space  under  the  stopper 
of  about  an  inch.  Rinse  off  the  stopper  with  flowing  water; 
put  it  into  the  bottle  while  still  wet  and  secure  it  by  tying  over 
it  a  clean  piece  of  cotton  cloth.  Seal  the  ends  of  the  string  on 
the  top  of  the  stopper.  Under  no  circumstances  touch  the  in- 
side of  the  neck  of  the  bottle  or  the  stem  of  the  stopper  with 
the  hand,  or  wipe  it  with  a  cloth. 

From  a  Stream,  Pond,  or  Reservoir.  —  Rinse  the  bottle  and 
stopper  with  the  water,  if  this  can  be  done  without  stirring  up 
the  sediment  on  the  bottom.  Then  sink  the  bottle,  with  the 
stopper  in  place,  entirely  beneath  the  surface  of  the  water  and 
take  out  the  stopper  at  a  distance  of  twelve  inches  or  more  be- 
low the  surface.  When  the  bottle  is  full  replace  the  stopper, 
below  the  surface  if  possible,  and  secure  it  as  directed  above. 
It  will  be  found  convenient,  in  taking  samples  in  this  way,  to 
have  the  bottle  w^eighted  so  that  it  will  sink  below  the  surface, 
and  to  remove  the  stopper  with  a  cord.  It  is  important  that  the 
sample  should  be  obtained  free  from  the  sediment  at  the  bottom 
of  a  stream  and  from  the  scum  on  the  surface.  If  a  stream 
should  not  be  deep  enough  to  admit  of  this  method  of  taking  a 
sample,  dip  up  the  water  with  an  absolutely  clean  vessel  and 
pour  it  into  the  bottle  after  the  latter  has  been  rinsed. 

The  sample  of  water  should  be  collected  immediately  before 
shipping  by  express,  so  that  as  little  time  as  possible  shall  inter- 
vene between  the  collection  of  the  sample  and  its  examination. 
All  possible  information  should  be  furnished  concerning  the 
source  of  the  water  and  of  possible  sources  of  contamination. 
*  Ann.  Re  pi.  Mass.  State  Board  of  Health,  1890,  p.  520. 


WATER:    ANALYTICAL  METHODS  7 1 

For  example,  in  the  case  of  a  well,  the  proximity  of  dwellings, 
cesspools,  or  drains  should  be  recorded,  and  the  character  and 
slope  of  the  soil,  whether  toward  or  away  from  the  well,  should 
be  noted.  In  the  case  of  a  surface-water,  mention  any  ab- 
normal or  unusual  conditions;  as,  for  instance,  if  the  streams 
or  ponds  are  swollen  by  recent  heavy  rains,  or  are  unusually  low 
in  consequence  of  prolonged  drought,  or  if  there  be  a  great  deal 
of  vegetable  growth  in  or  on  the  surface  of  the  water.  Record, 
in  short,  any  circumstantial  evidence  which  by  any  possibility 
may  aid  in  the  final  judgment. 

TJie  question  of  proper  collection  of  samples  is  an  important  one, 
and  the  chemist  is  perfectly  justified  in  refusing  to  give  an  opinion 
in  regard  to  the  purity  of  a  water  which  he  has  not  himself  collected. 

Preparation  for  Analysis.  —  Since  changes  in  the  composition 
of  a  contaminated  water  are  constantly  going  on,  the  analysis  of 
the  sample  should  be  begun  without  delay.  The  bottle  is  held 
under  the  tap,  and  the  neck  and  stopper  are  washed  free  from 
adhering  dust.  The  stopper  is  rinsed  off  with  some  of  the  water 
from  the  bottle. 

If  the  sample  has  stood  for  several  hours,  allowing  suspended 
matter  to  settle,  the  conditions  of  turbidity  and  sediment,  as  de- 
scribed on  page  108,  may  first  be  observed.  The  sample  is  then 
thoroughly  mixed  and  qualitative  tests  made  for  alkalinity, 
ammonia  and  chlorides.  Make  the  alkalinity  test  with  methyl 
orange  indicator.  If  a  sample  is  acid,  it  is  necessary  to  make 
alkaHne,  as  described  later,  before  starting  the  determinations 
for  free  ammonia  and  chlorides.  IMake  the  test  for  ammonia 
by  adding  two  c.c.  of  Nessler  reagent  to  50  c.c.  of  the  sample  in 
a  Nessler  tube.  A  reddish-brown  color  or  precipitate  means  the 
presence  of  large  amounts  of  ammonia,  and  care  should  be  taken 
not  to  take  too  much  of  the  sample  for  the  quantitative  deter- 
mination (see  page  74).  A  qualitative  test  for  chlorides  will 
determine  the  amount  of  water  to  be  taken  for  the  analysis,  — 
a  very  slight  opalescence  meaning  low  chlorides,  which  will 
necessitate  the  use  of  a  250-c.c.  sample,  while  a  distinct  tur- 
bidity or  a  precipitate  will  allow  a  25-c.c.  sample  to  be  used. 


72  AIR.   WATER,   AND   FOOD 

As  the  nitrogen  compounds  are  more  subject  to  important 
changes  than  any  others,  it  is  desirable  to  make  these  determi- 
nations first,  the  order  of  the  remainder  being  immaterial. 

It  is  essential  that  the  sample  of  water  be  thoroughly  mixed 
each  time  any  is  withdrawn,  as  only  in  this  way  will  the  samples 
removed  be  of  constant  composition.  This  is  particularly  im- 
portant in  dealing  with  sewages  and  sewage  effluents,  or  where 
there  is  a  considerable  amount  of  suspended  matter. 

The  methods  for  preparing  standard  solutions  and  other 
special  reagents  will  be  found  in  Appendix  B. 

Determinations  of  Free  and  Albuminoid  Ammonia.  —  Am- 
monia occurs  in  waters  as  ammonium  salts,  —  carbonate,  chlo- 
ride, or  nitrate.  In  sewages  it  may  be  partially  present  as  the 
hydroxide.  On  boiling  an  alkaline  solution  of  these  substances, 
the  salts  are  decomposed,  as  well  as  some  unstable  organic  com- 
pounds such  as  urea,  and  ammonia  passes  off  and  dissolves  in 
the  condensed  steam.  The  ammonia  thus  collected  is  called  the 
"free  ammonia."  If,  now,  alkaline  potassium  permanganate  is 
added  to  the  water  left  after  the  free  ammonia  has  been  removed, 
and  the  boiling  continued,  part  of  the  nitrogenous  organic  mat- 
ter will  be  decomposed  with  the  liberation  of  ammonia.  This 
is  termed  "  albuminoid  ammonia." 

The  principles  involved  in  the  two  determinations  have  been 
described  in  the  above  definitions,  that  is,  the  water  is  first 
boiled,  and  the  steam  condensed  until  all  the  free  ammonia 
has  been  removed.  Then  alkaline  potassium  permanganate  is 
added,  and  distillation  continued  until  no  more  albuminoid 
ammonia  is  evolved.  The  ammonia  is  determined  in  the  dis- 
tillates by  means  of  Nessler  reagent  which  gives  a  greenish 
yellow  with  very  small  amounts  of  ammonia,  and  yellow  to  red- 
dish brown  with  larger  quantities.  The  exact  amount  of  am- 
monia is  obtained  by  comparison  of  the  colors  obtained  with 
those  from  known  amounts  of  ammonia. 

Nessler  reagent  is  a  solution  of  potassium  mercuric  iodide 
(K2Hgl4)  containing  potassium  hydroxide.  The  colored  sub- 
stance formed  when  this  reacts  with  ammonia  is  dimercuram- 


WATER:    ANALYTICAL  METHODS 


73 


monium  iodide  (NHg2l  •  H2O),  which  is  an  ammonium  iodide  in 
which  the  hydrogen  atoms  have  been  substituted  by  mercury. 
This  substance  is  sHghtly  soluble  in  an  excess  of  potassium  iodide 
and  potassium  hydroxide,  giving  a  color  proportional  to  the 
amount  of  ammonia  present. 

Apparatus  and  Reagents.  —  The  apparatus  consists  of  a 
750  c.c.  round-bottomed  flask,  having  square  shoulders  and  a 
narrow  neck  five  inches   long,   and  an   ordinary  Liebig   con- 


FiG.  8. 

denser  fitted  with  a  block-tin  inner  tube  -f^  of  an  inch  in  diam- 
eter which  extends  just  through  a  cork  stopper  closing  the 
flask.  The  apparatus  is  set  so  that  the  distillate  may  be  col- 
lected directly  in  a  50  c.c.  Nessler  tube.  The  flasks  are  heated 
either  with  the  free  flame  of  a  Bunsen  burner  or  with  an  electric 
flask  heater.  These  latter  are  somewhat  slow  in  heating  up 
and  in  cooling,  but  give  an  even  heat  with  just  about  the  proper 
rate  of  distillation  and  show  little  tendency  to  cause  "  bump- 
ing." In  place  of  the  Liebig  condenser,  the  tin  tube  may  be 
passed  through  a  copper  or  galvanized  iron  tank  (see  Fig.  8), 


74  AIR,  WATER,  AND   FOOD 

fitted  with  proper  inlets  and  outlets,  and  serving  as  a  con- 
denser for  a  number  of  flasks.  New  flasks  are  treated  with 
boiling  dilute  sulphuric  acid  and  potassium  bichromate  before 
they  are  used.  New  corks  should  be  steamed  out  for  one  or 
two  hours.  A  good  sound  cork  will  last  for  several  months 
with  daily  use. 

The  Nessler  tubes  used  should  be  of  the  same  height  up  to 
the  50  c.c.  mark. 

Reagents  necessary  are  Nessler  solution,  alkaline  potassium 
peniianganate,  a  standard  ammonium  chloride  solution  and 
ammonia-free  water  (see  Appendix  B). 

Procedure.  —  Free  the  apparatus  from  ammonia  by  placing 
500  c.c.  of  ammonia-free  water  in  the  flask  and  distilling.  Col- 
lect the  distillate  in  50  c.c.  Nessler  tubes,  and  test  each  tube  as 
it  is  filled,  by  adding  two  c.c.  of  Nessler  reagent  and  comparing 
the  color  obtained  after  waiting  five  minutes  with  that  obtained 
by  adding  two  c.c.  of  Nessler  reagent  to  50  c.c.  of  ammonia-free 
water.  This  latter  gives  a  zero  standard.  Continue  until  the 
distillate  is  free  from  ammonia  and  then  pour  the  water  left  in 
the  flask  into  the  bottle  marked  "  ammonia-free  residues." 

While  this  is  going  on  make  a  qualitative  test  on  the  sample 
of  water  to  determine  the  amount  which  should  be  used  for  the 
quantitative  determination.  To  do  this,  add  to  100  c.c.  of  the 
water,  removed  from  the  bottle  only  after  thorough  mixing, 
one  c.c.  of  10  per  cent  copper  sulphate  solution,  and  one  c.c.  of 
50  per  cent  potassium  hydroxide.  Allow  to  settle  and  filter 
through  a  dry  paper  into  a  50  c.c.  Nessler  tube,  discarding  the 
first  10  c.c.  of  filtrate.  Add  two  c.c.  of  Nessler  reagent,  and 
allow  to  stand  for  10  minutes.  Make  a  standard  by  placing 
two  c.c.  of  the  standard  ammonium  chloride  solution  in  a  Nessler 
tube,  making  up  to  50  c.c.  with  ammonia-free  water,  mixing 
thoroughly  and  adding  two  c.c.  of  Nessler  reagent.  If  the  color 
obtained  from  the  sample  of  water  is  less  than  this  standard, 
use  a  500  c.c.  sample  of  the  water  for  the  determination;  if 
equal  to  or  greater  than  the  standard,  use  a  100  c.c.  sample; 
if  the  color  is  so  deep  that  a  precipitate  forms,  use  a  lo-c.c. 


WATER:    ANALYTICAL   METHODS  75 

sample.  For  sewages  five  or  10  c.c.  are  sufficient.  In  case  less 
than  500  c.c.  are  used,  dilute  the  amount  to  this  volume  with 
ammonia-free  water. 

Test  some  of  the  water  with  methyl  orange  for  acidity.  If 
acid,  0.5  gram  of  pure  sodium  carbonate  must  be  added  before 
starting  the  distillation.  The  great  majority  of  drinking  waters 
are  alkaline,  but  once  in  a  while  an  acid  water  turns  up,  and  it 
is  well  to  be  on  the  lookout.  Acid  sewages  and  sewage  filter 
effluents  are  not  uncommon. 

When  the  apparatus  has  been  freed  from  ammonia,  shake 
thoroughly  the  bottle  containing  the  water  sample,  and  measure 
out  in  a  calibrated  flask  500  c.c,  or  a  smaller  amount,  according 
to  the  quahtative  test  described  above,  adding  enough  ammonia- 
free  water  to  make  the  total  volume  at  least  500  c.c,  and 
pour  into  the  distilling  flask.  If  necessary,  add  sodium  car- 
bonate. Distill  three  portions  of  50  c.c.  each  into  well-rinsed 
Nessler  tubes.  Regulate  the  height  of  the  flame  so  that  the 
time  of  distilling  50  c.c.  shall  not  be  more  than  eight  and  not 
less  than  five  minutes.  In  most  cases  three  portions  are  suffi- 
cient to  collect  all  the  free  ammonia,  but  it  is  well  to  test  the 
last  portion  with  Nessler  reagent,  and  compare  it  with  a  zero 
ammonia  standard,  before  proceeding  further.  Save  these  por- 
tions for  nesslerization,  as  they  contain  all  the  free  ammonia. 

After  the  free  ammonia  has  been  distilled  off,  allow  the  con- 
tents of  the  flask  to  cool  for  10  minutes;  then  add  40  c.c.  of 
alkaline  pennanganate  through  a  funnel,  taking  care  that  none 
of  the  alkahne  solution  touches  the  neck  of  the  flask,  and  pro- 
ceed with  the  distillation  of  the  albuminoid  ammonia.  With 
colored  waters  distill  off  five  portions  of  50  c.c.  each;  with 
colorless  waters,  three  or  four  portions  will  suffice.  These 
portions  contain  the  albuminoid  ammonia. 

Unless  permanent  standards  are  used,  prepare  standards  by 
adding  to  Nessler  tubes  nearly  filled  with  ammonia-free  water 
varying  quantities  of  the  standard  ammonium  chloride  solution ; 
for  instance,  o.i,  0.3,  0.5,  0.7,  i.o,  1.3,  1.5,  2.0,  2.5,  4.0,  6.0  c.c 
The  standard  ammonium  chloride  solution  contains  0.0000 1  2;ram 


76 


AIR,   WATER,   AND    FOOD 


N  in  one  cubic  centimeter.  Mix  the  contents  of  the  tubes  by  ro- 
tating them  between  the  palms  of  the  hands  or  by  pouring  into 
another  Nessler  tube  and  back  again  (never  shake  them  Hke  a 
test-tube  or  stir  them  with  a  rod),  allow  them  to  stand  for  a  few 
minutes  and  add  two  c.c.  of  Nessler  reagent  to  each  tube  and 
to  each  of  the  portions  of  distillate.  At  the  end  of  lo  minutes 
match  the  colors  and  record  the  amount  of  ammonia  in  terms 
of  cubic  centimeters  of  the  standard  ammonium  chloride  solu- 
tion. From  the  value  of  this  solution  calculate  the  amounts  of 
free  and  albuminoid  ammonia  as  parts  of  nitrogen  per  million 
of  water. 

As  an  example,  the  following  results  from  distilling  500  c.c. 
may  be  given. 


Free  ammonia. 

Albuminoid  Ammonia. 

ist    50  C.C. 
2nd  50  C.C. 
3d      50  C.C. 

,          0.7  CC. 

0.3  C.c 

,        0.0  C.c. 

ist    50  C.C,          4.5  C.C. 
2nd  50  c.c,         2.8  c.c. 
3d    50  c.c,         1.5  c.c. 
4th  50  c.c,         1 .0  c.c. 
5th  50  c.c,        0.5  c.c 

i.o  c.c. 

10.3  c.c. 

In  this  case,  the  free  ammonia  would  be  0.020  and  the  albumi- 
noid ammonia  0.206  parts  per  million. 

In  dealing  with  sewages  or  sewage  effluents,  which  are  very 
high  in  free  ammonia,  if  the  ammonia  were  collected  in  three 
portions,  so  much  would  distill  over  in  the  first  portion  that  the 
color  given  with  the  Nessler  reagent  would  often  be  too  deep  to 
read  or  a  precipitate  might  form.  To  avoid  this,  the  total  dis- 
tillate of  150  to  175  c.c.  is  collected  in  a  200-c.c.  graduated  flask, 
made  up  to  the  mark,  thoroughly  mixed  by  pouring  into  a  clean 
dry  beaker  and  back  again,  and  then  50  c.c.  of  it  taken  for 
nesslerization.  In  this  way,  the  ammonia  is  distributed  more 
evenly  in  the  distillate  and  the  determination  is  not  sacrificed. 

If  free  ammonia  only  is  desired  in  a  sewage  or  sewage  effluent, 
a  direct  determination  is  to  be  preferred  over  distfllation.     For 


WATER:    ANALYTICAL  METHODS  77 

this,  proceed  as  directed  in  the  c^ualitative  test  for  ammonia,  ex- 
cept that  a  smaller  amount  of  the  filtrate  should  be  used,  two 
or  five  c.c,  and  this  made  up  to  50  c.c.  with  ammonia-free  water, 
treated  with  Nessler  reagent,  and  matched  against  standards 
as  just  described. 

Notes.  —  Where  a  large  number  of  determinations  are  made 
at  frequent  intervals,  permanent  Nessler  standards  are  a  great 
convenience.  These  should  be  made  according  to  directions 
found  in  "  Standard  Methods,"*  but  should  be  adjusted  by 
comparison  with  nesslerized  standards  made  from  ammonium 
chloride  solution. 

It  is  impossible  to  convert  all  of  the  organic  nitrogen  into 
ammonia  by  boiling  with  alkaline  permanganate.  The  amount 
of  ammonia  which  is  thus  obtained  depends  not  only  upon  the 
character  of  the  substances,  but  also  upon  the  concentration  of 
the  solution  and  the  rate  of  boiling.  In  order  that  the  albu- 
minoid ammonia  in  potable  waters  shall  bear  some  definite 
relation  to  the  total  organic  nitrogen,  it  is  necessary  that 
conditions  shall  be  duplicated  as  nearly  as  possible  in  differ- 
ent determinations;  that  is,  the  alkaline  permanganate  must  be 
added  to  a  definite  volume  of  water,  and  the  boiling  must  be 
carried  on  at  a  definite  rate.  Some  of  the  highly-colored  surface- 
waters  give  up  their  nitrogen  very  slowly  by  this  treatment; 
polluted  waters,  on  the  other  hand,  yield  the  ammonia  more 
rapidly,  so  that  the  observation  of  the  relative  amounts  found 
in  the  successive  portions  is  of  the  utmost  importance  in  form- 
ing a  judgment. 

A  depth  of  color  given  by  six  c.c.  pf  the  standard  ammonium 
chloride  with  the  Nessler  reagent  is  about  the  limit  of  satisfactory 
comparison  in  the  ii-inch  50  c.c.  tubes.  The  color  given  by 
10  or  12  c.c.  of  the  standard  may  be  matched  in  the  100  c.c.  tubes 
with  a  depth  of  five  inches  and  a  diameter  of  i^  inches. 

For  most  cases,  where  great  exactness  is  not  essential,  it  is 
possible  to  divide  the  50  c.c.  or  the  100  c.c.  portion  into  two 

*  "Standard  Methods  of  Water  .\nalysis,"  American  Public  Health  .\sso- 
ciation,  1912,  p.  17. 


78  AIR,  WATER,   AND   FOOD 

equal  parts  by  pouring  into  a  tube  the  exact  counterpart  of  the 
standard  tube  and  matching  the  color.  It  is  even  possible  to 
approximate  closely  the  correct  result  by  the  use  of  a  foot  rule. 
The  standard  is,  we  will  assume,  five  c.c.  The  height  of  the 
liquid  in  the  tube  to  be  tested  we  will  call  nine  inches.  If  the 
height  of  the  column  left  which  matches  five  c.c.  is  three  inches, 
then  the  reading  was  15  c.c.  of  the  standard. 

The  limit  of  solubility  of  the  mercur-ammonium  iodide  is 
reached  at  25  or  30  c.c.  of  the  standard  in  50  c.c.  The  incipient 
precipitate  not  only  changes  the  color  of  the  solution,  but  causes 
a  slight  milkiness  or  turbidity  which  prevents  a  sharp  reading 
of  the  color. 

The  test  is  an  excellent  example  of  quantitative  color  work 
when  carried  out  under  strictly  comparable  conditions. 

It  should,  perhaps,  be  stated  that  in  both  the  ammonium  and 
nitrate  determinations,  as  also  in  that  of  iron,  dilution  of  the 
sample  in  which  the  color  is  already  developed  does  not  give  a 
correct  result.  Therefore  dilution,  if  necessary,  must  be  made 
before  the  reagents  are  added. 

In  order  to  secure  the  most  accurate  results,  it  is  important 
that  the  temperature  of  the  distillates  to  be  nesslerized  and  of 
the  standards  be  the  same,  since  the  warmer  solutions  give  a 
more  intense  color  with  the  Nessler  reagent. 

Total  Organic  Nitrogen,  Kjeldahl  Process.  —  The  principles 
involved  in  the  method  consist  in  the  oxidation  of  the  carbon 
and  hydrogen  of  the  organic  matter  with  boiling  sulphuric  acid, 
the  nitrogen  being  converted  into  ammonia  and  held  by  the  acid 
as  ammonium  sulphate.  The  ammonia  is  then  liberated  and 
distilled  off  from  an  alkaline  solution. 

Apparatus  and  Reagents.  — The  apparatus  used  is  that  shown 
in  Fig.  9.  This  is  an  arrangement  for  distilling  with  steam. 
The  reagents  needed  are  nitrogen-free  sulphuric  acid  and  potas- 
sium hydroxide  (see  Appendix  B). 

Procedure.  —  Measure  500  c.c.  of  the  water  into  a  round- 
bottomed  flask  of  750  c.c.  capacity  and  boil  until  about  200  c.c. 
have  been  driven  off.     (The  free  ammonia  which  is  thus  ex- 


WATER:    ANALYTICAL   METHODS 


79 


pelled  may  be  determined,  if  desired,  by  connecting  the  flask 
with  a  condenser.)  Allow  the  water  remaining  in  the  flask  to 
cool,  and  add  lo  c.c.  of  pure  concentrated  sulphuric  acid  free 
from  nitrogen.  Mix  by  shaking; 
place  the  flask  in  an  inclined  posi- 
tion on  wire  gauze  under  the  hood 
and  boil  cautiously  until  the  water 
is  all  driven  oft".  Place  a  small 
funnel  in  the  neck  of  the  flask  to 
prevent  the  escape  of  acid  fumes, 
and  continue  the  heating  for  at 
least  half  an  hour  after  the  sul- 
phuric acid  becomes  white.  Mean- 
while, rinse  out  the  distilling  ap- 
paratus and  free  it  from  ammonia 
as  usual.  Then,  after  the  acid  in 
the  digestion  flask  has  cooled,  rinse 
down  the  neck  of  the  flask  with 
loo  c.c.  of  ammonia-free  water  and 
attach  the  flask  to  the  distillation 
apparatus.  Add  loo  c.c.  of  potas- 
sium hydroxide  solution  through 
the  separatory  funnel  and  distill 
off  the  ammonia  with  steam,  re- 
ceiving the  distillate  in  a  250-c.c.  graduated  flask.  Conduct 
the  distillation  rather  slowly  until  the  first  50  c.c.  have  distilled 
over,  then  distill  more  rapidly  until  about  175  c.c.  have  been 
collected.  Make  the  volume  of  the  distillate  up  to  250  c.c. 
with  ammonia-free  water,  mix  it  thoroughly  and  take  50  c.c. 
for  nesslerization. 

The  use  of  mercury  and  of  potassium  permanganate  to  assist 
in  the  oxidation  has  been  found  to  be  unnecessary,  as  the  organic 
matter  in  natural  waters  is  much  more  easily  oxidized  than  in 
other  substances,  —  flour,  for  instance.  The  presence  of  nitrates 
and  nitrites  in  waters  has  not  been  found  to  interfere  with  the 
accurate   determination  of    the  organic    nitrogen.     The  error, 


Fig. 


8o  AIR,  WATER,  AND   FOOD 

which  has  been  found  by  Kjeldahl  and  Warrington  to  be  caused 
by  the  presence  of  nitrates  seems  to  disappear  when  the  organic 
material  is  diluted  to  the  considerable  extent  that  exists  in 
natural  waters.  The  high  chlorine  found  in  some  well-waters 
does  not  interfere  with  the  method  to  any  extent,  but  this  de- 
termination does  not  possess  much  value  in  this  class  of  waters, 
which  are  low  in  organic  nitrogen. 

In  carrying  out  the  digestion  with  sulphuric  acid,  the  greatest 
care  must  be  taken  to  prevent  access  of  ammonia  or  dust  from 
any  source.  The  acid  solutions  will  absorb  ammonia  from  the 
air  or  from  the  dust  of  the  laboratory  if  they  are  allowed  to  re- 
main uncovered  for  any  length  of  time.  This  source  of  error 
may  in  some  instances  be  sufhciently  large  to  render  a  determi- 
nation valueless,  even  in  a  room  which  is,  to  all  appearances,  free 
from  ammonia-fumes.  Hence,  the  operation  should,  if  possible, 
be  carried  to  completion  within  twenty-four  hours,  and  for  every 
set  of  determinations  a  blank  analysis  should  be  made  with  am- 
monia-free water  in  order  to  make  a  correction  for  the  ammonia 
in  the  reagents,  and  for  that  accidentally  introduced  during  the 
process. 

As  the  result  of  many  hundred  comparative  determinations 
of  the  organic  nitrogen  and  of  the  albuminoid  ammonia  in  nat- 
ural waters  which  take  their  origin  in  the  glacial  drift,  it  has 
been  found  that  the  nitrogen  given  by  the  albuminoid-ammonia 
process,  as  directed  in  the  previous  pages,  is  about  one-half  of  the 
total  organic  nitrogen  as  given  by  the  Kjeldahl  process;  in  the 
case  of  sewages  and  polluted  waters,  it  is  very  variable  owing  to 
their  irregular  composition. 

Determination  of  Nitrogen  in  the  Form  of  Nitrites. — This  de- 
termination depends  on  the  formation  of  a  pink  azo  dye  by  the 
interaction  of  sulphanilic  acid,  naphthylamine  acetate,  and  nitrous 
acid.  If  an  excess  of  the  first  two  reagents  is  used,  the  amount 
of  dye  and,  therefore,  the  depth  of  color  will  be  proportional  to 
the  amount  of  nitrite  present  in  the  water.  The  color  is  then 
compared  with  a  series  of  standards  made  from  a  sodium  nitrite 
solution  of  known  strength  and  the  nitrite  computed  in  terms  of 
nitrogen. 


WATER:    ANALYTICAL  METHODS  8l 

The  reactions  which  take  place  are,  first,  the  diazotizing  of  the 
sulphanilic  acid  by  the  nitrous  acid  present,  and  then  the  inter- 
action of  this  diazo  compound  with  naphthylamine  to  form  the 
colored  substance,  a-naphthylamine-para-azo-benzene-para-sul- 
phonic  acid. 

/NH2 
C6H4  +  C10H7NH2  +  HNO2  -> 

'^SOsH 

/     N  =  N     ^ 
CioHe^  C6H4  +  2H2O. 

^  NHo     SO3H  ^ 

Apparatus  and  Reagents.  —  The  only  special  apparatus  needed 
is  a  number  of  100  c.c.  Nessler  tubes.  The  reagents  used  are  a 
standard  sodium  nitrite  solution  (i  c.c.  contains  o.ooooooi 
gram  nitrogen),  a  solution  of  sulphanilic  acid  in  acetic  acid,  a 
solution  of  naphthylamine  acetate,  and  a  suspension  of  alumi- 
num hydroxide  (see  Appendix  B). 

Procedure.  —  If  the  water  is  colorless,  measure  out  100  c.c. 
into  a  loo-c.c.  Nessler  tube.  If  the  water  possesses  color  which 
cannot  be  removed  by  simple  filtration,  it  should  be  decolorized 
as  follows:  Thoroughly  rinse  with  the  water  a  250-c.c.  glass- 
stoppered  bottle;  pour  into  it  about  200  c.c.  of  the  sample, 
add  about  three  c.c.  of  milk  of  alumina  and  shake  the  bottle  vig- 
orously. Let  stand  for  10  or  15  minutes  and  filter  through  a 
small  plaited  filter  which  has  been  thoroughly  washed  with 
water  free  from  nitrites.  To  100  c.c.  of  the  filtered  sample  or  of 
the  originally  colorless  water  add  10  c.c.  of  the  sulphanilic  acid 
in  acetic  acid  and  10  c.c.  of  naphthylamine  acetate  solution. 
A  pink  color  shows  the  presence  of  nitrite.  To  detennine  the 
amount*  of  nitrite  present  make  up  standards  by  placing  5  c.c, 
10  c.c,  15  c.c,  and  20  c.c.  each  of  the  standard  nitrite  solution 
in  loo-c.c  Nessler  tubes.  Make  up  to  100  c.c.  with  nitrite-free 
water,  mix  by  pouring  into  a  Nessler  tube  and  back  to  the  original 
tube,  and  then  add  the  reagents  as  before.    Allow  to  stand  10 

*  Standard  color  papers  and  also  acid  solutions  of  fuchsine  are  used  for  nitrite 
standards.     Neither  of  these  has  been  found  very  satisfactory  in  this  laboratory. 


82  AIR,   WATER,   AND   FOOD 

minutes,  and  match  with  the  color  obtained  from  the  water 
sample.  If  this  does  not  match  any  of  the  standard  colors, 
make  up  intermediate  standards.  Do  not  attempt  to  match 
colors  closer  than  to  one  c.c.  of  the  nitrite  solution.  If  the 
color  is  deeper  than  that  given  by  20  c.c.  of  the  standard  nitrite 
solution,  start  a  new  determination  using  a  smaller  quantity  of 
water  and  diluting  to  100  c.c.  with  the  ammonia-free  water. 

One  c.c.  of  the  standard  nitrite  solution  equals  o.ooooooi 
gram  nitrogen.  Determine  the  number  of  c.c.  needed  to  match 
the  color  obtained  from  the  water  sample  and  calculate  the 
results  in  parts  of  nitrogen  per  million  of  water. 

Notes.  —  In  case  the  color  obtained  is  deeper  than  20  c.c.  of 
the  standard,  an  aliquot  part  may  be  measured,  as  described 
under  the  ammonia  determination.  This. will  be  sufficiently 
accurate  for  most  purposes. 

When  once  obtained,  the  color  will  remain  unchanged  for  one- 
hah  to  three-quarters  of  an  hour.  If  left  for  a  longer  time,  the 
nitrites  absorbed  from  the  air  will  noticeably  increase  the  color. 

Determination  of  Nitrogen  in  the  Form  of  Nitrates.*  —  This 
determination  depends  on  the  action  of  nitric  acid  on  phenol- 
disulphonic  to  form  nitrophenoldisulphonic  acid,  which  gives 
an  intensely  yellow  color  in  alkaline  solution.  The  reactions 
involved  can  be  expressed  as  follows: 


/OH 
CeHs  -  SO3H  +  HNO3  -^      C6H2  <  gQ^g  +  H2O 

\n02 


OH 

\SO3H 
.OH 


/ 


SO3H 


OK 
SO3K 


'-'^^^^  SO3H+  3  KOH  ->     CeHo  <  l)?^  +  3  H2O 

Reagents.  —  The  reagents  needed  are  a  standard  nitrate  solu- 
tion of  which  one  c.c.  contains  o.oooooi  gram  nitrogen,  and  phe- 

*  Sprengel,  Fogg,  Ann.,  1863,  121,  p.  188;  Grandval  and  Lajoux,  Compt.  rend., 
1865,  loi,  p.  62;  Gill,  J.  Am.  Chem.  Soc,  1894,  16,  p.  122;  Chamot  &  Pratt,  /. 
Am.  Chem.  Soc,  1909,  31,  p.  922;  1910,  32,  p.  630;  Chamot,  Pratt  and  Redfield, 
/.  Am.  Chem.  Soc,  1911,  33,  p.  366. 


WATER:    ANALYTICAL  METHODS  83 

noldisulphonic  acid  (see  Appendix  B).  Care  should  be  taken 
in  making  this  latter  reagent  as  the  results  are  dependent  upon 
its  composition. 

Procedure.  —  For  ground  waters,  measure  with  a  pipette  two 
samples  of  the  water,  one  of  two  c.c.  and  the  other  of  five  c.c, 
into  three-inch  porcelain  evaporating  dishes  and  evaporate  just 
to  dryness  on  the  steam  bath  or  electric  plate  run  at  low  heat. 
For  surface-waters  use  10  c.c.  If  the  water  is  colored,  decolor- 
ize with  alumina  as  described  under  nitrites.  Do  not  allow  the 
residue  to  remain  on  the  steam  bath  after  all  the  water  has  been 
evaporated.  Cool,  add  six  drops  of  phenoldisulphonic  acid  and 
rub  with  a  glass  rod  to  insure  complete  contact  of  the  acid  and 
residue.  Then  add  seven  c.c.  of  distilled  water  and  three  c.c.  of 
30  per  cent  potassium  hydroxide  solution  and  mix  thoroughly.  A 
yellow  color  shows  the  presence  of  nitrates.  Place  this  solution 
in  a  short  Nessler  tube*  for  comparison  with  a  standard.  This 
standard  is  prepared  as  follows:  Place  one  c.c.  of  potassium  hy- 
droxide solution  in  a  short  Nessler  tube  and  add  standard  nitrate 
solution  from  a  burette  until  the  color  of  the  standard  nearly 
matches  that  of  the  water  sample.  Make  the  volumes  of  the 
two  solutions  equal  by  diluting  the  standard  and  then  add  more 
standard  nitrate  solution  until  the  colors  exactly  match.  Use 
the  sample  of  water  for  comparison  which  has  the  lighter  color, 
unless  there  is  no  yellow  at  all.  In  case  the  five  c.c.  sample 
gives  no  color,  repeat  the  determination,  using  10  c.c.  If  this 
gives  no  color  nitrates  are  absent.  If  the  two  c.c.  sample  gives 
a  color  which  requires  more  than  10  c.c.  of  the  standard,  repeat 
the  determination,  using  smaller  amounts  of  water. 

The  standard  nitrate  solution  contains  0.00000 1  gram  N  per 
c.c.  From  the  amounts  of  standard  nitrate  solution  and  of 
water  used  calculate  the  amount  of  nitrate  present  expressed  as 
nitrogen  in  parts  per  million  of  water. 

Notes.  —  High  chlorides  seriously  affect  the  accuracy  of  the 
method.  This  is  noticeable  in  dealing  with  sea  water  and  deep 
wells  which  contain  large  amounts  of  sodium  chloride.  In  this 
*  An  ordinar>-  50-c.c.  Nessler  tube  cut  off  to  a  length  of  about  five  inches. 


84  AIR,   WATER,   AND   FOOD 

case,  the  reduction  method  with  alkali  and  aluminum  foil  and 
distillation  of  the  ammonia  formed,  is  to  be  recommended.*  For 
most  drinking  waters  it  is  not  necessary  to  use  this  method, 
which  requires  a  much  longer  time  than  that  described  above. 

Determination  of  Chlorine.  —  Chlorine  is  present  in  waters 
in  the  form  of  chlorides,  and  the  term  "chlorine"  is  used  to 
mean  "  chlorides  "  as  the  results  of  analysis  are  given  in  terms 
of  chlorine. 

The  determination  is  made  by  titration  with  silver  nitrate  in 
a  solution  alkahne  with  bicarbonates,  —  the  condition  generally 
existing  in  natural  w'aters,  —  potassium  chromate  being  used  as 
an  indicator. 

Reagents.  —  The  solutions  required  are  a  standard  sodium 
chloride  solution  (i  c.c.  contains  o.ooi  gram  CI),  a  solution  of 
silver  nitrate  about  one-half  as  strong,  and  potassium  chromate 
indicator  (see  Appendix  B). 

Procedure.  —  Standardize  the  silver  nitrate  solution  b}^  ti- 
trating against  a  standard  sodium  chloride  solution.  To  do  this 
place  25  c.c.  of  distilled  water  in  a  6-inch  porcelain  evaporating 
dish,  add  three  drops  of  potassium  chromate  indicator,  and  then 
run  in  from  a  burette  a  measured  amount  of  sodium  chloride 
solution,  about  live  c.c.  being  sufficient.  It  is  not  necessary  to 
add  exactly  five  c.c,  but  it  is  necessary  to  know  the  exact  amount 
added.  Now  add  silver  nitrate  solution  from  a  burette  until 
the  yellow  color  of  the  solution  has  changed  to  a  faint  reddish 
brown.  The  end  point  is  best  seen  if  25  c.c.  of  distilled  water 
and  three  drops  of  indicator  are  placed  in  a  6-inch  dish  which 
is  set  beside  the  dish  in  which  the  titration  is  being  carried  on. 
This  gives  a  standard  color  and  the  end  point  is  reached  when 
the  solution  being  titrated  shows  the  slightest  appearance  of 
red  as  compared  with  the  standard.  From  the  results  of  the 
standardization  calculate  the  value  of  silver  nitrate  solution  in 
terms  of  sodium  chloride  solution  and  in  terms  of  CI  per  c.c. 

Test  the  water  to  be  analyzed  with  phenolphthalein  and  with 
methyl  orange.     It  should  be  acid  to  the  former  and  alkaline 

*  See  "Standard  Methods,"  p.  25. 


WATER:    ANALYTICAL  METHODS  85 

to  the  latter.  If  alkaline  to  phenolphthalein  neutralize  the 
sample  measured  for  titration  with  dilute  sulphuric  acid.  If 
acid  to  methyl  orange  neutralize  with  sodium  bicarbonate. 

Highly  colored  waters  should  be  decolorized  before  titration 
as  the  color  interferes  with  the  end  point.  To  do  this  shake 
some  of  the  sample  in  an  Erlenmeyer  flask  with  milk  of  alu- 
mina, one  c.c.  of  the  latter  being  used  for  each  100  c.c.  of  water. 
Heat  the  mixture  rapidly  to  boiling,  allow  to  settle  and  decant 
through  a  filter. 

Make  a  qualitative  test  for  chlorides  on  the  sample  of  water. 
If  only  a  faint  opalescence  appears,  a  250  c.c.  sample  must  be 
used  for  analysis;  if  a  marked  cloudiness  or  a  precipitate  is 
formed,  a  25  c.c.  sample  may  be  used.  If  the  larger  sample  is 
found  to  be  necessary,  evaporate  to  about  25  c.c.  on  a  steam 
bath  or  electric  plate;  avoid  boiling.     Cool  before  titrating. 

To  25  c.c.  of  the  water,  measured  wdth  a  pipette,  or  an  evap- 
orated 250  c.c.  sample,  in  a  6-inch  porcelain  dish,  add  three  drops 
of  indicator  and  about  five  c.c.  of  sodium  chloride  solution,  the 
exact  amount  being  measured  as  in  the  standardization.  Then 
run  in  silver  nitrate  solution  until  the  end  point  is  reached, 
using  the  standard  color  as  before. 

From  the  amounts  of  silver  nitrate  and  sodium  chloride  solu- 
tions used  calculate  the  amount  of  chlorine  present  in  parts  per 
million. 

Notes.  —  With  waters  containing  large  amounts  of  chlorides, 
the  addition  of  sodium  chloride  in  the  titration  may  be  omitted. 

It  is  important  that  the  process  be  carried  out  essentially  as 
described,  since  it  has  been  found  that  the  results  vary  with 
the  volume  of  solution  in  which  the  titration  is  made,  the  amount 
of  chromate  used,  and  the  amount  of  precipitated  chloride  pres- 
ent.* 

Determination  of  the  Carbonaceous  Matter  or  "  Oxygen 
Consumed."  —  This  determination  is  supposed  to  give  the 
amount  of  oxygen  absorbed  by  the  organic  matter  present  in 
the  water.     Except  in  sewage  analysis,  the  results  are  of  little 

*  Hazen,  Am.  Chem.  J .,  1889,  11,  p.  409. 


86  AIR,   WATER,  AND  FOOD 

importance,  and  the  determination  may  be  omitted  without 
appreciably  aflfecting  the  interpretation  of  the  results  of  the 
whole  analysis. 

The  oxygen  consumed  is  determined  by  allowing  an  excess 
of  potassium  permanganate  in  acid  solution  to  act  on  the  or- 
ganic matter  in  the  water  under  certain  conditions,  and  then 
titrating  the  excess  of  permanganate  with  ammonium  oxalate. 
Equations: 
4  KMn04  +  6  H2SO4  +  5  C  -^  2  K2SO4  +  4  MnS04  +  6  H2O 

+  5  CO,. 
2  KMn04  +  3  H2SO4  +  5  C2H2O4 .  2  H2O  -^  K2SO4  +  2  MnS04 
+  10CO2  +  18H2O. 

Reagents.  —  The  solutions  required  are  a  standard  ammo- 
nium oxalate  solution  (i  c.c.  equals  o.oooi  gram  oxygen),  a 
potassium  permanganate  solution  of  approximately  the  same 
strength,  and  1-3  sulphuric  acid  (see  Appendix  B). 

Procedure.  KuheVs  Hot  Acid  Method.  —  Standardize  the 
potassium  permanganate  against  the  oxalate  in  the  following 
way:  Measure  100  c.c.  of  distilled  water  into  a  250-c.c.  flat- 
bottomed  flask,  add  10  c.c.  of  sulphuric  acid  (1-3)  and  then  add 
from  a  burette  a  measured  quantity  (about  10  c.c.)  of  standard- 
ized potassium  permanganate  solution.  Place  the  flask  on  a 
wire  gauze  or  electric  stove  and  heat  quickly  to  boiling.  Boil 
the  solution  gently  for  exactly  five  minutes,  remove  it  from  the 
flame,  cool  for  one  minute,  and  add  from  a  burette  sufficient 
ammonium  oxalate  to  decolorize  the  solution.  Titrate  back 
with  the  permanganate  to  a  faint  permanent  pink  color.  Cal- 
culate the  value  of  the  permanganate  in  terms  of  standard 
ammonium  oxalate  and  of  oxygen. 

For  the  analysis  proceed  just  as  in  the  standardization,  re- 
placing the  distilled  water  by  the  sample  to  be  tested.  The 
oxygen  consumed  value  for  the  water  under  examination  is 
obtained  from  the  number  of  c.c.  of  permanganate  used  in 
excess  of  that  required  to  react  with  the  oxalate  added  in  the 
determination.  Calculate  the  results  in  parts  of  oxygen  per 
million  of  water. 


WATER:    ANALYTICAL  METHODS  87 

Notes.  ■ —  For  highly  colored  surface-waters  25  c.c.  are  taken 
and  diluted  to  100  c.c.  with  w-ater  free  from  organic  matter;  for 
sewages,  10  c.c.  or  less  are  diluted  in  the  same  way. 

The  oxygen  given  up  by  the  permanganate  combines  with  the 
carbon  of  the  organic  matter  and  perhaps,  to  a  certain  extent, 
with  the  hydrogen,  but  not  with  the  nitrogen.  The  amount  of 
oxygen  consumed  bears  some  relation,  therefore,  to  the  amount 
of  organic  carbon  present  in  the  water,  but  this  relation  cer- 
tainly cannot  be  taken  as  a  definite  one  in  every  case,  the  results 
varying  even  with  the  time  of  boihng.  The  method  has  its 
greatest  value  when  it  is  used  to  compare  waters  of  the  same 
general  character  and  having  the  same  origin;  for  example,  in 
making  periodical  tests  of  the  purity  of  the  effluent  from  a  filter. 
Furthennore,  in  order  that  the  results  shall  have  this  compara- 
tive value,  it  is  absolutely  necessary  that  the  process  shall 
always  be  carried  out  in  exactly  the  saine  way,  even  to  the 
minutest  detail  of  quantity,  time  and  temperature. 

In  some  cases  it  may  be  found  advantageous  to  heat  the  solu- 
tion upon  the  water-bath  for  half  an  hour  instead  of  boiling  it 
for  five  minutes.  The  results,  however,  will  not  be  exactly 
comparable  with  those  obtained  by  boiling. 

Different  kinds  of  organic  matter  behave  differently  with 
various  oxidizing  agents,  so  that  a  comparison  of  the  results 
obtained  with  different  oxidizing  agents  may  throw  light  upon 
the  character  of  the  organic  matter,  as  w^ell  as  its  amount.* 
In  waters  from  the  watersheds  of  eastern  North  America  the 
color  and  the  oxygen  consumed  have  a  certain,  though  some- 
what varying,  relation. 

Determination  of  the  Residue  on  Evaporation  and  the  Loss 
on  Ignition.  —  Procedure.  —  Carefully  clean  a  large  platinum 
dish,  ignite  for  a  few  minutes  over  a  burner,  cool  in  a  desiccator 
and  weigh.  Measure  into  it  100  c.c.  of  the  water  (200  c.c.  in 
the  case  of  surface-waters),  and  evaporate  to  dryness  on  the 
water-bath.  WTien  the  water  is  all  evaporated,  heat  the  dish 
in  the  oven  at  the  temperature  of  boiling  water  for  one  hour, 
*  Woodman,  /.  Am.  Client.  Soc,  189S,  20,  p.  497. 


88  AIR,   WATER,   AND   FOOD 

cool  in  a  desiccator  over  sulphuric  acid,  and  weigh.  The  increase 
in  weight  gives  the  'Hotal  solids"  or  "residue  on  evaporation." 

The  residue  should  be  ignited  and  the  loss  on  ignition  noted. 
Heat  the  dish  in  a  "radiator,"  which  consists  of  another  plat- 
inum dish  enough  larger  to  allow  an  air-space  of  about  half  an 
inch  between  the  two  dishes,  the  inner  dish  being  supported  by 
a  triangle  of  platinum  wire.  Over  the  inner  dish  is  suspended 
a  disc  of  platinum-foil  to  radiate  back  the  heat  into  the  dish. 
The  larger  platinum  dish  is  heated  to  bright  redness  by  a  triple 
gas-burner.  An  electric  mufHe  may  be  used  in  place  of  the  radi- 
ator. This  should  be  run  at  a  temperature  of  about  500°  C. 
Heat  the  dish  until  the  residue  is  white  or  nearly  so.  Note  any 
blackening  or  charring  of  the  residue  and  any  peculiar  "burnt 
odor"  which  may  be  given  off.  After  the  dish  has  cooled, 
slightly  moisten  the  residue  with  a  few  drops  of  distilled  water. 
Heat  the  residue  in  the  oven  for  an  hour;  cool  in  a  desiccator 
and  weigh.  This  gives  the  weight  of  "fixed  solids,"  the  differ- 
ence being  the  "loss  on  ignition."  Save  the  residue  for  the  de- 
termination of  iron. 

Notes.  ■ —  Before  the  introduction  of  modern  methods  of  water- 
analysis,  the  determination  of  "loss  on  ignition"  was  the  only 
method  for  the  estimation  of  organic  matter  in  water.  In 
order,  however,  that  the  determination  shall  possess  any  real 
value,  it  is  necessary  to  regulate  carefully  the  heat  during  the 
ignition,  so  as  to  destroy  the  organic  matter  without  decompos- 
ing calcium  carbonate  or  volatilizing  the  alkali  chlorides. 

This  is  what  the  use  of  the  radiator  or  muffle  is  intended  to 
accomplish,  and  in  the  case  of  surface-waters  with  low  mineral 
content  and  considerable  organic  matter,  the  method  gives  gen- 
erally satisfactory  results.  But  in  the  case  of  ground  waters 
having  little  or  no  organic  matter  and  high  mineral  content, 
the  loss  is  often  very  great  on  account  of  the  decomposition  of 
nitrates  and  chlorides  of  the  alkaline  earths  and  the  loss  of  water 
of  crystallization.  In  waters  of  this  class,  the  determination  of 
"loss  on  ignition"  is,  therefore,  generally  meaningless,  although 
an  approximation  to  the  amount  of  organic  matter  can  be  ob- 


WATER:    ANALYTICAL  METHODS  89 

tained  by  the  addition  of  sodium  carbonate  to  the  water  before 
evaporating  to  dryness.  By  this  means,  the  alkaline  earths  are 
precipitated  as  carbonates,  the  chlorine  and  nitric  acid  are  held 
by  an  alkaHne  base,  and  there  is  no  water  of  crystallization  in 
the  residue.  Even  with  this  modification,  the  loss  is  consider- 
able when  magnesium  salts  are  present,  owing  to  the  evolution  of 
carbonic  acid. 

It  is  the  practice  in  some  laboratories  to  ignite  over  a  direct 
flame,  taking  care  that  the  dish  does  not  reach  a  temperature 
above  a  faint  redness. 

The  behavior  on  ignition  is  oftentimes  significant.  Swampy 
or  peaty  waters  give  a  brownish  residue  on  evaporation  to  dry- 
ness, which  blackens  or  chars,  and  this  black  substance  burns 
off  quite  slowly.  The  odor  of  the  charring  is  like  that  of  char- 
ring wood  or  grain;  sometimes  sweetish,  but  not  at  all  offensive. 
Waters  much  polluted  by  sewage  blacken  slightly;  the  black 
particles  burn  off  quickly  and  the  odor  is  disagreeable.  Any 
observations  on  this  point  should  be  recorded  in  the  report. 

Determination  of  Iron.  —  This  depends  on  the  color  produced 
by  the  action  of  potassium  sulphocyanate  on  ferric  chloride. 
The  color  obtained  is  compared  with  standards. 

Reagents.  —  The  solutions  needed  are  a  i-i  hydrochloric 
acid,  a  potassium  sulphocyanate  solution,  and  a  standard  iron 
solution  made  from  ferrous  ammonium  sulphate,  one  c.c.  of 
this  containing  o.oooi  gram  iron  (see  Appendix  B). 

Procedure.  —  Treat  the  residue  from  the  loss  on  ignition,  or 
that  obtained  by  the  evaporation  of  100  c.c.  of  the  water,  with 
five  c.c.  of  i-i  hydrochloric  acid,  warming  on  the  steam-bath 
or  hot  plate  so  as  to  dissolve  as  much  as  possible  of  the  mineral 
matter.  Wash  the  solution  with  distilled  water  into  a  loo-c.c. 
Nessler  tube,  filtering  if  there  is  any  insoluble  matter.  Make 
up  to  about  50  c.c.  with  distilled  water.  Add  potassium  per- 
manganate solution,  a  few  drops  at  a  time,  until  the  solution 
remains  pink  for  10  minutes.  This  is  to  oxidize  any  ferrous 
chloride  to  the  ferric  condition.  Then  add  10  c.c.  of  potassium 
sulphocyanate  solution  and  make  the  volume  up  to  the  100  c.c. 


90  AIR,   WATER,  AND   FOOD 

mark  with  distilled  water.  Iron  gives  a  red  color.  If  iron  is 
present  prepare  a  blank  standard  by  placing  75  c.c.  of  distilled 
water,  five  c.c.  of  hydrochloric  acid  and  10  c.c.  of  potassium 
sulphocyanate  solution  in  a  100  c.c.  Nessler  tube.  Now  add 
from  a  burette,  standard  iron  solution  until  the  color  nearly 
matches  that  obtained  in  the  determination.  Fill  the  tube  with 
distilled  water  to  the  100  c.c.  mark  and  continue  adding  the  iron 
solution  until  the  color  of  the  blank  exactly  matches  that  of  the 
determination.  From  the  number  of  c.c.  of  standard  iron  solu- 
tion used  calculate  the  amount  of  iron  in  the  w^ater. 

Notes.  —  In  the  case  of  some  river-waters,  it  will  be  found 
necessary  to  add  a  few  cubic  centimeters  of  hydrochloric  acid 
to  the  water  while  evaporating,  in  order  to  facilitate  the  solution 
of  the  iron.  This  should  be  done  on  a  separate  portion  from  that 
used  for  the  determination  of  total  solids. 

The  colors  should  be  matched  immediately  after  adding  the 
sulphocyanate,  since  the  color  fades  appreciably  on  standing. 
If  the  color  is  greater  than  that  given  by  3.5  c.c.  of  the  standard 
solution  an  aliquot  part  should  be  used.  In  this  case  sufficient 
hydrochloric  acid  and  potassium  sulphocyanate  should  be  added 
so  that  the  same  amounts  of  these  are  present  as  given  in  the 
above  directions. 

Determination  of  Hardness.  —  Soap  (Clark's)  Method. 
This  method  really  gives  the  soap  consuming  power  and  not 
the  true  total  hardness,  but  it  is  in  general  use  for  sanitary  pur- 
poses, and  where  the  water  is  to  be  used  for  household  purposes 
only,  really  gives  what  is  most  wanted.  The  determination 
depends  on  the  fact  that  soap  forms  an  insoluble  precipitate 
with  the  calcium  and  magnesium  salts  in  the  water.  As  soon 
as  the  precipitation  of  the  latter  is  complete  a  permanent  lather 
is  formed.  This  serves  as  the  end  point.  The  hardness  is 
expressed  in  terms  of  calcium  carbonate  per  million. 

Reagent.  —  A  standard  soap  solution  (see  Appendix  B). 

Procedure.  —  Measure  50  c.c.  of  water  into  a  200-c.c.  clear 
glass-stoppered  bottle  and  add  the  soap  solution  from  the  burette, 
two  or  three  tenths  of  a  cubic  centimeter  at  a  time,  shaking  well 


WATER:    ANALYTICAL  METHODS  9I 

after  each  addition,  until  a  lather  is  obtained  which  covers  the 
entire  surface  of  the  liquid  with  the  bottle  lying  on  its  side,  and 
is  permanent  for  five  minutes.  The  number  of  parts  of  calcium 
carbonate  corresponding  to  the  volume  of  soap  solution  used  is 
found  in  the  table  in  Appendix  A. 

Notes.  —  The  importance  of  adding  the  soap  in  small  quan- 
tities cannot  be  too  strongly  emphasized,  especially  in  the  pres- 
ence of  magnesium  compounds.  The  presence  of  magnesium 
salts  will  be  recognized  by  the  pecuUar  curdy  appearance  of 
the  precipitate  formed  and  by  the  occurrence  of  a  false  end  point, 
the  lather  lasting  about  three  minutes  when  the  titration  is 
about  half  done. 

By  reference  to  the  table  it  will  be  observed  that  values  are  not 
given  for  more  than  16  c.c.  of  the  soap  solution.  If  in  any  case 
the  water  under  examination  requires  more  than  10  c.c.  of  the 
standard  soap  solution,  a  smaller  portion  of  25  c.c,  10  c.c.  or 
even  two  c.c,  as  the  case  may  require,  is  measured  out  and  made 
up  to  a  volume  of  50  c.c.  with  recently  distilled  water.  If  the 
volume  of  soap  used  is  always  about  seven  c.c,  this  will  keep 
the  results  comparable  with  each  other,  although  the  element 
of  dilution  introduces  an  error.  Potable  waters,  in  the  eastern 
United  States,  at  least,  are  rarely  so  high  in  mineral  matter  as 
to  require  excessive  dilution.  In  the  case  of  extremely  hard 
waters,  however,  the  acid  method  is  to  be  preferred.  Distilled 
water  itself,  containing  no  calcium  salt  whatever,  requires  the 
use  of  a  considerable  quantity  of  soap  to  produce  a  permanent 
lather.  The  cause  for  this  seems  to  exist  in  the  dissociation 
of  the  greater  part  of  the  soap  at  the  extreme  dilution  to  which 
it  is  subjected,  and  the  slow  accumulation  of  a  sufficient  quantity 
of  undissociated  soap  to  allow  of  the  increase  of  surface  tension 
to  a  point  at  which  soap-bubbles  will  persist. 

Hehner^s  Acid  MetJiod*  —  The  temporary  hardness  of  a  water 
is  that  part  of  the  total  hardness  which  can  be  removed  by 
boiling.     It  is  due  to  the  presence  of  the  bicarbonates  of  calcium 

*  Hehner,  A)ialyst,  1SS3,  8,  p.  77;  Draper,  Clicm.  A^cics,  1885,  51,  p.  206;  Ellms, 
/.  Am.  Chan.  Soc,  1899,  21,  p.  239. 


92  AIR,  WATER,  AND   FOOD 

and  magnesium.  These  give  an  alkaline  reaction  to  indicators 
such  as  methyl  orange  and  erythrosine,  and  can  be  titrated 
with  standard  acid.  The  results  obtained  will  differ  slightly 
from  the  true  temporary  hardness,  on  account  of  the  solubility 
of  calcium  and  magnesium  carbonates  which  are  formed  when  a 
solution  of  the  bicarbonates  is  boiled,  but  the  results  are  close 
enough  for  practical  purposes. 

Permanent  hardness  is  that  which  is  not  removed  by  boiHng, 
and  is  due  mainly  to  the  presence  of  the  sulphates  and  chlorides 
of  calcium  and  magnesium.  After  removing  the  temporary 
hardness  by  boiling,  the  permanent  hardness,  i.e.,  the  calcium 
and  magnesium  remaining  in  solution,  may  be  determined  by 
adding  standard  "soda  reagent"  (a  mixture  of  equal  parts  of 
sodium  hydroxide  and  sodium  carbonate),  which  precipitates 
the  magnesium  as  hydroxide  and  the  calcium  as  carbonate. 
The  excess  of  soda  reagent  added  is  then  determined  by  titration 
with  standard  acid,  —  the  amount  consumed  representing  the 
calcium  and  magnesium. 

If  the  original  water  is  neutralized  with  sulphuric  acid  all  the 
temporary  hardness  will  be  converted  to  permanent  hardness. 
If  this  latter  is  then  determined,  it  will  represent  the  total  hard- 
ness of  the  sample  of  water. 

Reagents.  —  The  solutions  required  for  the  hardness  deter- 
minations are  N/20  and  N/50  sulphuric  acid,  N/io  soda  reagent, 
methyl  orange  indicator  and,  for  some  purposes,  erythrosine. 

Procedure  for  Alkalinity.  —  Measure  200  c.c.  of  the  sample, 
filtered  if  necessary,  into  a  porcelain  evaporating  dish,  add  two 
drops  of  methyl  orange  indicator  and  titrate  to  a  faint  pink  with 
N/50  sulphuric  acid.  The  end  point  can  best  be  seen  by  placing 
200  c.c.  of  distilled  water  in  another  dish  and  adding  two  drops 
of  indicator.  This  gives  a  standard  color  and  the  first  change 
of  the  sample  being  titrated,  toward  a  pink  color,  can  be  readily 
recognized.  The  number  of  c.c.  of  acid  used  multiplied  by  five 
gives  the  alkalinity  in  parts  of  calcium  carbonate  per  million. 
Save  the  titrated  sample  for  the  determination  of  total  hardness. 

If  the  soap  hardness  is  over  300,  a  100  c.c.  sample  should  be 


WATER:    ANALYTICAL  METHODS  93 

used.  In  this  case  multiply  the  c.c.  of  acid  by  10  to  get  the 
alkalinity. 

Notes.  —  If  the  water  to  be  tested  has  been  treated  with  alum, 
erythrosine  indicator  must  be  used  as  methyl  orange  is  not 
sufficiently  sensitive.  For  this,  measure  100  c.c.  of  the  water 
into  a  clear  bottle  such  as  is  used  for  the  soap  test,  and  add  2.5 
c.c.  of  the  erythrosine  indicator  (o.i  gram  of  the  sodium  salt  in 
one  liter  of  distilled  water),  and  five  c.c.  of  chloroform  neutral 
to  erythrosine.  Mix  well  by  shaking  and  add  N/50  sulphuric 
acid  from  a  burette  in  small  quantities,  shaking  thoroughly 
after  each  addition.  The  pink  color  in  the  water  gradually 
grows  lighter  until  the  addition  of  a  drop  or  two  of  the  acid 
causes  it  to  disappear  entirely.  Make  a  correction  for  the  indi- 
cator by  carrying  out  a  blank  determination  with  distilled  water. 
]Multiply  the  c.c.  of  acid  used  by  10  to  get  the  alkalinity  in  terms 
of  calcium  carbonate. 

Procedure  for  Permanent  Hardness.  —  Measure  200  c.c.  of 
water  into  an  Erlenmeyer  flask,  boil  10  minutes  to  expel  carbon 
dioxide,  and  add  25  c.c.  of  N/io  soda  reagent.  For  waters 
with  a  soap  hardness  over  300  use  a  100  c.c.  sample.  Boil 
down  to  a  volume  of  about  100  c.c,  cool  to  20°  C,  rinse  into  a 
200  c.c.  calibrated  flask  with  cooled,  boiled  distilled  water,  and 
make  up  to  200  c.c.  Mix  thoroughly.  Filter  through  a  dry 
filter  paper,  receiving  the  filtrate  in  a  100  c.c.  calibrated  flask. 
Discard  the  first  30  or  40  c.c,  and  then  collect  100  c.c.  of  the 
filtrate.  Pour  into  an  Erlenmeyer  flask,  add  one  drop  of  methyl 
orange  indicator  and  titrate  with  N/20  sulphuric  acid. 

Make  a  blank  determination  with  200  c.c.  of  distilled  water 
in  place  of  the  sample. 

The  difference  between  the  amount  of  acid  required  by  the 
blank  and  that  required  in  the  determination  represents  the 
amount  of  soda  reagent  used  to  precipitate  the  calcium  and  mag- 
nesium. To  get  the  penuanent  hardness  multiply  this  difler- 
ence  by  25  when  a  200  c.c.  sample  of  water  is  used. 

If  a  water  contains  sodium  or  potassium  carbonate  there  wiU 
not  be  any  permanent  hardness,  and  hence  more  acid  will  be 


94  AIR,  WATER,  AND   FOOD 

required  for  the  filtrate  than  corresponds  to  the  amount  of 
soda  reagent  added.  From  this  excess  the  amount  of  sodium 
carbonate  in  the  water  may  be  determined.  Any  alkah  carbon- 
ate present  would  be  calculated  as  temporary  hardness  by  the 
direct  titration;  hence  it  should  be  calculated  to  calcium  car- 
bonate and  subtracted  from  the  results  found  by  the  direct 
titration. 

Procedure  for  Total  Hardness.  —  Boil  down  the  neutralized 
sample  obtained  at  the  end  of  the  alkalinity  determination  to 
about  loo  c.c,  add  25  c.c.  soda  reagent,  again  boil  down  to  100 
c.c,  and  proceed  as  in  the  determination  of  permanent  hardness. 
The  calculations  are  the  same  as  described  there. 

Free  Carbonic  Acid.  —  This  determination  depends  on  the 
reaction  of  sodium  carbonate  with  carbon  dioxide  to  form  the 
bicarbonate, 

NasCOs  +  H2O  +  COo  ->  2  NaHCOa. 
As  soon  as  all  the  free  carbonic  acid  has  been  used  up,  the  next 
drop  of  sodium  carbonate  will  color  phenolphthalein  red. 

Reagents.  —  These  are  an  N/22  sodium  carbonate  solution, 
and  phenolphthalein  indicator. 

Procedure.  —  Measure  100  c.c.  of  the  sample  into  a  tall,  narrow 
vessel,  preferably  a  100  c.c.  Nessler  tube,  add  a  few  drops  of 
phenolphthalein  and  titrate  rapidly  with  N/22  sodium  carbonate 
solution,  stirring  gently  until  a  faint  but  permanent  pink  color 
is  produced. 

The  number  of  c.c.  of  N/22  sodium  carbonate  solution  used 
in  titrating  100  c.c.  of  water,  multiplied  by  10,  gives  the  parts  per 
million  of  free  carbonic  acid  as  CO2. 

Note.  —  Owing  to  the  ease  with  which  free  carbonic  acid  escapes 
from  water,  particularly  when  present  in  considerable  quantities, 
it  is  highly  desirable  that  a  special  sample  should  be  collected  for 
this  determination,  which  should  preferably  be  made  on  the 
ground.  If  this  cannot  be  done,  approximate  results  from 
water  not  high  in  free  carbonic  acid  may  be  obtained  from 
samples  collected  in  bottles  which  are  completely  filled  so  as  to 
leave  no  air  space  under  the  stopper. 


WATER:    ANALYTICAL  METHODS  95 

Determination  of  Sulphates.*  —  Sulphates  can  be  determined 
with  an  accuracy  sufficient  for  most  purposes  by  means  of  the 
Jackson  Candle  Turbidimeter.!  The  results  are  determined  by 
the  amount  of  turbidity  produced  by  precipitated  barium  sul- 
phate. 

Procedure.  —  To  about  100  c.c.  of  the  water  add  sufficient 
dilute  hydrochloric  acid  (about  one  c.c.)  to  acidify  and  then 
one-half  a  gram  of  barium  chloride.  Shake  until  dissolved. 
Pour  slowly  into  the  graduated  tube  of  a  candle  turbidimeter 
until  the  image  of  the  flame  beneath  just  disappears.  Read  the 
height  of  the  liquid  in  the  turbidimeter  tube  and  obtain  from 
the  table  in  Appendix  A  the  parts  per  million  of  sulphates  as  SO3. 

Notes.  —  Care  should  be  taken  to  have  the  solution  well 
stirred  before  adding  to  the  turbidimeter  tube.  The  tube  must 
not  be  placed  over  the  flame  when  empty.  Waters  containing 
from  30  to  200  parts  per  million  may  be  read  directly;  otherwise 
the  water  should  either  be  concentrated  or  diluted. 

Determination  of  Alum.  —  On  account  of  the  use  of  alum  or 
aluminum  sulphate  as  a  coagulant  in  the  filtration  of  water,  a 
determination  of  alumina  in  the  effluent  water  is  often  neces- 
sary.    This  may  be  readily  made  by  the  logwood  test.| 

Procedure.  —  The  logwood  solution  is  made  as  follows:  Take 
two  grams  of  logwood  chips  and  boil  one  minute  in  a  platinum 
dish  with  50  c.c.  of  distilled  water.  Decant  the  solution  and 
boil  again  for  one  minute  with  50  c.c.  of  water.  Decant  this 
and  similarly  boil  a  third  time  with  50  c.c.  of  water.  Decant 
this  into  a  platinum  receptacle  for  use.  Take  three  drops  for 
each  test.  Kept  in  platinum,  the  solution  will  last  for  several 
days  at  least. 

Test  the  water  as  follows:  Boil  50  c.c.  of  the  water  in  a  plat- 
inum dish  for  a  short  time  to  expel  carbon  dioxide.     Add  three 

*  "Laboratory  Notes  on  Industrial  Water  Analysis,"  Ellen  H.  Richards.  1910. 
J.  I.  D.  Hinds,  /.  Am.  Client.  Soc,  18,  661  and  22,  269;  D.  D.  Jackson,  J.  Am. 
Chem.  Soc,  1901,  p.  799;  Muer,  /.  lud.  Eiig.  Clieni.,  1911,  3,  p.  553. 

t  For  a  description  of  this  see  references. 

t  E.  H.  Richards,  TecJi.  Quart.,  1891,  4,  p.  194;  A.  H.  Low,  Tccli.  Quart.,  1902, 
15.  P-  351- 


96  AIR,  WATER,  AND   FOOD 

drops  of  the  logwood  solution  and  continue  boiling  for  a  few 
seconds  to  develop  the  color.  Decant  into  a  glass  flask  and 
cool  quickly  under  the  tap  (so  as  not  to  keep  the  hot  solution 
too  long  in  the  glass).  Transfer  to  a  No.  2  beaker  and  blow  in 
carbon  dioxide  from  the  breath  by  means  of  a  glass  tube  until 
there  is  no  further  decolorization.  Pour  the  water  into  a  Nessler 
tube  for  comparison  with  standards  similarly  prepared  from  a 
standard  alum  solution.  Allow  them  to  stand  several  hours 
before  taking  the  final  reading.  No  wash-water  is  used  at  any 
of  the  decantations.  The  test  shows  one  part  of  aluminum 
sulphate  in  8,000,000  parts  of  water. 

Notes.  —  A  blank  made  with  distilled  water,  if  not  completely 
decolorized  by  the  CO2,  will  show  a  tint  perceptibly  fainter  than 
that  produced  by  one  part  in  8,000,000  of  aluminum  sulphate. 

It  should  be  noted  that  carbon  dioxide  must  be  kept  absent 
until  the  point  prescribed.  The  solution  is,  therefore,  transferred 
to  a  beaker  in  order  to  keep  the  flask  free  from  carbon  dioxide  for 
the  next  test. 

The  main  points  are: 

1.  Any  kind  of  logwood  appears  to  answer. 

2.  The  solution  is  good  for  several  days,  at  least,  if  kept  in 
platinum. 

3.  The  use  of  platinum  instead  of  glass  for  boiling  the  test 
solution. 

4.  The  use  of  carbon  dioxide  instead  of  acetic  acid. 

Aluminum  hydrate,  as  pointed  out  in  1893  by  the  late  Profes- 
sor A.  R.  Leeds,  will  produce  a  tint  almost  as  strong  as  if  it 
were  in  solution,  but  of  a  distinctly  differing  tint. 

Low's  method  of  procedure  is  as  follows:  First,  test  the 
water  as  above  described.  If  no  tint,  or  none  exceeding  that 
of  the  blank,  remains  after  standing  several  hours  or  over  night, 
that  is  sufficient.  If,  however,  a  tint  persists,  or  a  colored  pre- 
cipitate settles  out,  it  is  necessary  to  determine  if  this  is  due  to 
aluminum  hydrate.  Pour  a  sample  of  the  water  several  times 
through  a  double  Swedish  filter,  and  finally  test  the  filtrate.  If 
the  tint  produced  is  weaker  than  that  given  by  the  unfiltered 


WATER:    ANALYTICAL   METHODS  97 

water,  repeat  the  operation  on  a  fresh  portion  of  the  waler, 
using  the  same  filter,  and  continue  repeating  with  new  portions 
of  the  water  and  ahvays  using  the  same  filter,  until  it  is  apparent 
that  no  further  diminution  of  the  tint  can  be  effected. 

For  a  less  delicate  test  in  school  laboratories  where  platinum 
is  not  available,  the  following  alternativ'e  method  may  be  used: 

Dissolve  about  o.i  gram  pure  ha^matoxylin  in  25  c.c.  water; 
this  solution  will  keep  for  two  weeks  and  works  best  after  being 
made  several  hours.  To  50  c.c.  of  the  water,  placed  in  a  four- 
inch  porcelain  dish,  add  two  drops  of  the  ha^matoxylin  solution, 
allow  the  solution  to  stand  for  one  or  two  minutes,  then  add  a 
drop  of  20  per  cent  acetic  acid.  The  standards  are  prepared  at 
the  same  time,  using  50  c.c.  of  distilled  water  and  the  required 
amount  of  a  standard  alum  solution.  The  comparison  must  be 
made  immediately,  since  the  color  fades  on  standing.  In  this 
way  the  presence  of  one  part  of  aluminum  sulphate  in  five  mil- 
lion can  be  detennlned  directly  in  the  water  and  with  ease. 

Logwood  may  be  used  instead  of  the  ha^matoxylin,  the  solu- 
tion being  prepared  as  above. 

This  test  will  show  the  presence  of  all  soluble  salts  of  aluminum 
which  enter  into  combination  with  the  coloring  matter  of  the 
logwood  to  form  a  "lake." 

The  alkalies  and  alkaline  earths  give  a  purplish  color  with 
logwood  extract,  hence  the  test  for  alum  can  be  made  only  in 
acid  solution. 

Determination  of  Lead.  —  Lead  in  the  minute  quantities  in 
which  it  ordinarily  occurs  in  water  is  best  estimated  by  comparing 
the  color  of  the  sulphide  with  standards. 

Procedure.  —  If  the  water  is  colorless,  fill  a  100  c.c.  Xessler 
tube  to  the  mark,  acidify  with  a  few  drops  of  acetic  acid,  and 
add  from  a  glass  tube  one  drop  of  calcium  sulphide  solution. 
A  black  tint  to  the  precipitated  sulphur  shows  the  presence  of 
lead.  A  quantitative  estimate  may  be  made  by  comparison 
with  a  series  of  standards  made  from  a  standard  lead  solution. 

If  the  water  is  too  highly  colored  to  estimate  the  lead  directly, 
evaporate  three  or  four  liters  in  a  porcelam  dish  to  about  25  c.c, 


98  AIR,   WATER,   AND   FOOD 

add  10  c.c.  of  ammonium  chloride  solution  and  a  considerable 
excess  of  strong  ammonia.  Then  add  h}-drogen  sulphide  water 
and  allow  the  dish  to  stand  some  hours.  Boil  the  contents  of 
the  dish  for  a  few  moments  to  expel  the  excess  of  hydrogen 
sulphide,  and  filter.  The  precipitate  contains  all  the  lead,  iron, 
and  suspended  organic  matter,  also  copper  and  zinc  if  present, 
while  the  soluble  color  goes  into  the  filtrate.  Wash  once  with 
hot  water,  transfer  the  filter  to  the  original  dish,  and  dissolve 
the  sulphides  by  boiling  with  dilute  nitric  acid  (i  part  acid, 
sp.  gr.  1.2,  to  5  parts  water).  Filter  and  wash;  evaporate  to 
10-15  c.c,  cool,  add  5  c.c.  concentrated  sulphuric  acid  and  evap- 
orate until  copious  fumes  are  given  off.  Then,  if  the  original 
water  contained  less  than  0.25  part  iron  per  million,  add  acetic 
acid  and  ammonia,  boil,  filter  and  read  the  amount  of  lead  in 
the  alkaline  filtrate,  making  the  standards  also  alkaline  with 
ammonia. 

If  the  water  contained  over  0.25  part  iron,  wash  the  lead 
sulphate  into  a  beaker  with  alcohol  and  water,  and  let  it  settle 
overnight.  Filter,  wash  free  from  iron  with  50  per  cent  alcohol, 
dissolve  the  precipitate  by  boiling  with  ammonium  acetate, 
filter,  and  determine  the  lead  as  above. 

Note.  —  If  more  than  0.25  part  of  iron  is  present,  some  of 
the  lead  will  be  held  by  the  precipitated  ferric  hydroxide;  and 
if  25  parts  are  present,  all  of  the  lead  may  be  lost  in  this  way; 
hence  the  modification  of  the  method  in  the  presence  of  consider- 
able quantities  of  iron.* 

When  copper  is  also  present  it  is  detected  by  the  blue  color 
given  to  the  ammoniacal  filtrate  from  the  iron  precipitation. 

Determination  of  Phosphates,  f  —  Procedure.  —  Evaporate  50 
c.c.  of  the  water  and  three  c.c.  of  nitric  acid  (sp.  gr.  1.07)  to 
dryness  in  a  three-inch  porcelain  dish  on  the  water-bath.  Heat 
the  residue  in  an  oven  for  two  hours  at  the  temperature  of  boiling 
water.     Treat  the  dry  residue  with  50  c.c.  of  cold  distilled  water, 

*  EUms,  J.  Am.  Chem.  Soc,  1899,  21,  p.  359. 

t  Lepierre,  Bull.  Soc.  Chim.,  1896,  15,  p.  1213;  Woodman  and  Cayvan,  /.  Am. 
Chem.  Soc,  1901,  23,  p.  96;  Woodman,  ibid.,  1902,  24,  p.  735. 


WATER:  ANALYTICAL  METHODS  99 

added  in  several  portions  and  poured  into  the  comparison-tube. 
It  is  not  necessary  to  filter  the  solution.  Add  four  c.c.  of  ammo- 
nium molybdate  (50  grams  per  liter)  and  two  c.c.  of  nitric  acid, 
mLx  the  contents  of  the  tube  and  compare  the  color,  after  three 
minutes,  with  standards  made  by  diluting  varying  quantities 
of  the  standard  phosphate  solution  (i  c.c.  =  o.oooi  gram  P2O5) 
to  50  c.c.  with  distilled  water  and  adding  the  reagents  as  above. 
Carry  out  a  blank  determination  on  the  distilled  water  used  for 
dilution,  especially  if  it  has  stood  for  any  length  of  time  in  glass 
vessels. 

Notes.  —  The  method  as  described  will  be  sufficient  for  ordi- 
nary work.  If  a  more  exact  determination  of  the  phosphate  is 
required,  a  slight  correction  should  be  made  in  each  case.  For 
a  table  showing  these  corrections  reference  may  be  made  to  the 
paper  by  Woodman  and  Ca}"\^an  previously  cited. 

The  evaporation  and  heating  with  nitric  acid  is  for  the  purpose 
of  removing  silica,  which  gives  with  ammonium  molybdate  a 
yellow  color  similar  to  that  given  by  phosphates. 

The  determination  of  phosphates  in  a  drinking-water  is  a 
matter  which  has  not  received  the  attention  from  water  analysts 
that  has  been  given  to  the  estimation  of  various  other  con- 
stituents. Any  one  who  looks  through  the  literature  cannot 
help  noticing  how  few  are  the  published  results  of  quantitative 
estimations  of  the  phosphate  content  of  natural  waters,  apart 
from  mineral  waters.  Yet  this  determination,  by  reason  of  the 
conversion  of  organic  phosphorus  compounds  into  phosphates 
through  the  process  of  decay,  is  one  which  might  reasonably 
be  expected  to  throw  considerable  light  on  the  question  of  the 
pollution  of  natural  waters  by  objectionable  material. 

The  reasons  for  this  dearth  of  published  data  are  not  far  to 
seek.  To  be  of  value  the  amount  of  phosphate  must  be  known 
within  rather  narrow  limits.  Qualitative  tests  are  not  sufficient. 
The  mere  presence  of  phosphates  is  by  no  means  definite  or 
even  confirmatory  evidence  of  organic  pollution.  Rocks  and 
minerals  containing  phosphates  are  found  nearly  ever>"svhere, 
and  traces,  at  times  even  considerable  quantities,  may  be  dis- 


lOO  AIR,  WATER,  AND   FOOD 

solved,  especially  by  waters  rich  in  carbonic  acid.  This,  how- 
ever, does  not  constitute  a  serious  objection  to  the  utility  of  the 
determination.  The  same  is  true  of  many,  if  not  most,  of 
the  constituents  upon  which  reliance  is  placed  in  judging  of  the 
quahty  of  a  water.  Unpolluted  waters  often  contain  notable 
amounts  of  nitrates  and  chlorides,  and  a  true  judgment  can  be 
rendered  only  after  comparison  with  samples  from  adjacent 
but  unpolluted  sources. 

The  chief  reason,  however,  has  been  the  lack  of  an  accurate 
and  simple  method,  sufficiently  delicate,  and  of  enough  data 
to  work  out  a  standard  for  comparison. 

This  reason  can  hardly  hold  true  now,  for  enough  work  has  been 
done  on  the  colorimetric  method  to  indicate  its  value  as  another 
link  (of  which  we  have  none  too  many,  anyway)  in  the  chain  of 
circumstantial  evidence  by  which  we  are  often  compelled  to 
judge  the  purity  of  a  water. 

The  amount  of  phosphate  and  its  variation  seem  to  follow 
the  same  general  line  as  the  other  mineral  constituents  which 
either  accompany  the  polluting  material  or  are  produced  by  its 
decay,  especially  the  nitrates  and  chlorides.  It  is  not,  however, 
so  delicate  an  indicator  as  these.  In  general,  it  may  be  said 
that  the  amount  (expressed  as  P2O5)  in  an  unpolluted  water  will 
seldom  be  over  i.o  part  per  million. 

Determination  of  Dissolved  Oxygen.  —  Winkler  Method*  — - 
The  method  depends  on  the  absorption  of  oxygen  by  man- 
ganous  hydroxide  with  the  formation  of  manganese  dioxide; 
the  liberation  of  iodine  by  this  last  in  an  acid  solution  contain- 
ing potassium  iodide;  and  the  titration  of  the  iodine  with  sodium 
thiosulphate.  The  reactions  involved  can  be  expressed  as 
follows : 

MnS04  +  2  NaOH  -^  Mn  (0H)2  +  Na2S04. 

2  Mn(0H)2  +  O2  -^  2  Mn02  +  2  H2O. 

Mn02  +  2  H2SO4  +  2  KI  -^  MnS04  +  I2  +  K2SO4  +  2  H2O. 

2  NaoSaOs  +  lo  -^  2  Nal  +  Na2S406. 

*  Berichte,  1888,  21,  p.  2843;  also  see  "Standard  Methods  of  Water  Analysis." 


WATER:    ANALYTICAL   METHODS 


lOI 


The  method  has  recently  been  modified  by  Hale  and  Melia* 
by  titrating  the  iodine  in  an  acetic  acid  solution  in  order  to 
avoid  difficulties  due  to  the  presence  of  nitrites  and  nitrates, 
and  this  should  be  followed  in  testing  for  putrescibility. 

Collection  of  Samples.  —  The  samples  are  collected  in  glass- 
stoppered  bottles  of  known  capacity,  holding  about  300  cubic 
centimeters.  When  water  is  taken  from  a  faucet,  the  bottle 
is  filled  by  means  of  a  tube  which  passes  to  the  bottom  of  the 
bottle.  A  considerable  amount  of  water  is  allowed  to  pass 
through  the  bottle  and  overflow  at  the  top.  It  will  be  almost 
impossible  to  obtain  duplicate  samples  unless  the  bottles  are 
filled  at  the  same  time  by  means  of  a  T  tube,  owing  to  varia- 
tions in  pressure  in  the  pipes. 

In  taking  samples  from  a  stream  or  pond,  a  stopper  with  two 
holes  is  used.  A  tube  passing  through  one  of  these  holes  is 
sunk  in  the  water  to  the  desired  depth, 
and  the  other  is  connected  with  a  larger 
bottle  of  at  least  four  times  the  capacity 
of  the  smaller  one,  and  fitted  in  the  same 
way.  From  the  larger  bottle  the  air  is 
exhausted  by  the  lungs  or  by  an  air-pump 
until  it  is  nearly  filled  with  water.  Unless 
the  determination  is  to  be  made  at  once, 
the  rubber  stopper  of  the  smaller  bottle  is 
quickly  replaced  by  the  glass  stopper  so 
that  no  air  is  left  in  the  bottle.  The  tem- 
perature of  the  water  at  the  time  of  sam- 
pling should  be  noted. 

The  apparatus  which  has  been  used  in 
connection  with  work  in  this  laboratory 
for  collecting  samples  at  various  depths 
down  to  75  feet  is  shown  in  outline  in 
Fig.  10.  A  galvanized-iron  can  of  such 
size  as  to  hold  one  of  the  gallon  bottles  is  weighted  with 
lead  and  provided  with  ears  at  the  top  for  suspending.  The 
*  /.  Ind.  Eng.  Cliem.,  1913,  5,  p.  976. 


Fig.  10. 


I02  AIR,   WATER,   AND   FOOD 

bottle,  which  is  securely  wired  in,  is  provided  with  a  rubber 
stopper  carrying  two  brass  tubes,  one  ending  just  below  the 
stopper  and  projecting  for  about  8  or  9  inches  above  it,  the 
other  extending  to  the  bottom  of  the  bottle  and  connected  by 
heavy  rubber  tubing  with  the  sample  bottle.  This  is  held  by 
brass  brackets,  which  are  fastened  by  means  of  a  wooden  cleat 
to  the  side  of  the  can.  The  neck  of  the  bottle  is  put  into  the 
slot  in  the  upper  bracket  and  then  it  is  firmly  clamped  by  the 
thumb-screw  of  the  lower  one.  The  arrangement  of  tubes  in 
the  sample  bottle  is  obvious.  In  using  the  apparatus  it  is 
quickly  lowered  to  the  desired  depth  by  means  of  a  rope  marked 
off  in  feet.  The  water  enters  the  sample  bottle  and  flows  through 
it  into  the  other.  When  the  bubbles  cease  to  rise,  indicating 
that  the  larger  bottle  is  full,  thus  replacing  the  water  in  the  sam- 
ple bottle  a  number  of  times,  the  apparatus  is  drawn  to  the 
surface.  The  temperature  is  read  from  a  thermometer  fastened 
to  the  tube  inside  the  gallon  bottle. 

Reagents.  —  The  reagents  needed  are  solutions  of  man- 
ganous  sulphate,  potassium  iodide  in  sodium  hydroxide,  potas- 
sium acetate,  N/ioo  sodium  thiosulphate,  and  starch  indicator 
(see  Appendix  B). 

Procedure.  —  Remove  the  stopper  from  the  300-c.c.  cali- 
brated bottle,  and  add  two  c.c.  of  manganous  sulphate  solution 
with  a  pipette  having  a  long  capillary  point  reaching  to  the 
bottom  of  the  bottle,  and  in  the  same  way  add  two  c.c.  of  the 
solution  of  sodium  hydroxide  and  potassium  iodide.  Insert 
the  glass  stopper,  leaving  no  bubbles  of  air,  and  mix  the  contents 
of  the  bottle.  Allow  the  precipitate  to  settle,  remove  the  stopper 
and  add  two  c.c.  of  concentrated  hydrochloric  acid  from  a 
pipette  in  the  same  manner  as  before.  Replace  the  stopper, 
driving  out  some  of  the  liquid,  and  shake  until  the  precipitate 
is  dissolved,  and  the  Hquid  homogeneous.  Remove  100  c.c. 
with  a  pipette  or  graduated  flask,  and  titrate  with  N/ioo  sodium 
thiosulphate,  using  starch  as  an  indicator.  Add  the  starch 
solution,  about  two  c.c,  only  after  the  iodine  solution  has  be- 
come a  light  straw  color. 


WATER:    ANALYTICAL   METHODS 


103 


To  calculate  the  results  proceed  as  follows:  Let  V  equal  the 
volume  of  the  bottle  with  the  stopper  inserted  and  N  the  number 
of  c.c.  of  thiosulphate  used.  One  c.c.  of  N/ioo  sodium  thio- 
sulphate  is  equivalent  to  0.00008  gram  of  oxygen.  The  actual 
volume  of  water  from  which  the  oxygen  was  removed  is  equal 
to  the  volume  of  the  bottle  minus  the  four  c.c.  displaced  by  the 
first  two  reagents  added.  The  liquid  displaced  by  the  acid  does 
not  need  to  be  allowed  for,  as  it  did  not  contain  any  oxygen  or 
iodine.  The  oxygen  equivalent  to  the  iodine  titrated  in  the 
100  c.c.  of  the  solution  removed  is  equal  to  N  X  0.00008. 

The  oxygen  equivalent  to  the  total  iodine  liberated  is  equal  to 

N  X  0.00008  X  V 
100 

This  is  the  oxygen  present  in  the  original  water,  which  has  a 
volume  of  (F  —  4),  the  four  c.c.  being  the  part  displaced  by  the 
solutions  added.  The  oxygen  in  parts  per  million  is,  therefore, 
equal  to 

N  X  0.00008  X  F  X  1,000,000  ^  0.8  iVF 
100  X  (F  -  4)  ~  F  -  4  ' 

If  the  sodium  thiosulphate  solution  is  not  exactly  N/ioo,  the 
correct  oxygen  equivalent  should  be  substituted  in  place  of  the 
value  0.00008. 


QUANTITIES  OF  DISSOLVED  OXYGEN  IN  PARTS  PER  MILLION 

BY  WEIGHT  IN   WATER    SATURATED   WITH  AIR  AT  THE 

TEMPERATURE  GIVEN 


Temp. 
C. 

Oxygen. 

Temp. 
C. 

Oxygen. 

Temp. 
C. 

O.xygen. 

Temp. 

c. 

Oxygen. 

0 

14.70 

8 

11.86 

16 

9-94 

24 

8.51 

I 

14.28 

9 

11.58 

17 

9-75 

25 

8.35 

2 

13-88 

10 

II. 31 

18 

9  56 

26 

8.19 

3 

13  SO 

II 

11.05 

19 

9-37 

27 

8.03 

4 

13  14 

12 

10.80 

20 

9.19 

28 

7.88 

S 

12.80 

13 

10.57 

21 

9.01 

29 

7-74 

6 

12.47 

14 

10.35 

22 

8.84 

30 

7.60 

7 

12.16 

15 

10.14 

23 

8.67 





104  AIR,   WATER,   AND    FOOD 

The  results  of  this  determination  are  frequently  expressed  in 
per  cent  of  saturation,  which  is  given  by  the  ratio  of  the  oxygen 
found  to  that  present  if  the  water  were  completely  saturated 
at  the  same  temperature.  The  latter  figure  is  given  by  the 
preceding  table. 

Procedure  to  he  Followed  in  Putrescihility  Tests  or  with  Polluted 
Waters f^  — ■  Follow  the  directions  as  given  above  until  after  the 
addition  of  the  concentrated  hydrochloric  acid.  Then  replace 
the  stopper  and  shake  until  all  the  precipitate  is  dissolved. 
Remove  the  stopper  and  add  from  a  pipette  two  c.c.  of  potassium 
acetate  solution.  Mix  by  pouring  into  a  flask  or  beaker  and 
back  into  the  bottle.  Remove  loo  c.c.  as  before  and  titrate 
with  N/ioo  sodium  thiosulphate. 

The  addition  of  the  acetate  increases  the  volume  of  the  iodine 
solution  from  V  (the  volume  of  the  bottle)  to  (F  +  2),  and  this 
should  be  substituted  in  the  formula  given  on  p.  103.  The  oxygen 
in  parts  per  million  will,  therefore,  be  equal  to 

0.8  N  {V  +  2) 
F-4 

Notes.  —  If  water  is  collected  in  the  ordinary  way  and  trans- 
ferred to  the  apparatus  by  pouring,  there  will  inevitably  be 
an  absorption  of  oxygen  unless  the  water  is  already  saturated. 
Thus  a  process  which  gives  excellent  results  when  the  water  is 
nearly  or  quite  saturated  may  fail  entirely  to  give  accurate 
results  when  the  dissolved  oxygen  is  low  or  absent.  The  water 
may  be  supersaturated  with  oxygen  in  which  case  the  per  cent 
of  saturation  may  be  more  than  100. f 

Determinations  of  dissolved  oxygen  in  ponds  and  streams  are 
best  made  on  the  spot,  or,  at  least,  the  reagents  should  be  added 
until  after  the  addition  of  the  hydrochloric  acid.  The  very 
simple  apparatus  required  for  the  Winkler  process  can  be  packed 
in  a  small  space,  and  the  entire  determination  requires  only  a 
few  minutes.     The  absorption  of  the  oxygen  by  the  manganous 

*  See  article  by  Hale  and  Melia,  loc.  cit. 
t  Gill,  Tech.  Quart.,  1892,  5,  p.  250. 


WATER:    ANALYTICAL  METHODS  105 

hydroxide  is  complete  almost  at  once,  and  it  is  unnecessary  to 
allow  it  to  settle  for  a  long  time  before  adding  the  acid.  The 
titration  can  be  made  with  a  small  burette  or  pipette  with 
accurate  results. 

Putrescibility  Test.*  —  There  is  at  the  present  time  no  really 
satisfactory  standard  putrescibility  test.  One  which  seems  to 
have  been  worked  out  on  logical  principles  and  which  has  given 
satisfaction  in  this  laboratory  is  that  proposed  by  the  Royal 
Sewage  Commission.  The  putrescibility  is  measured  by  the 
absorption  of  dissolved  oxygen  under  given  conditions.  A 
stream  water  or  diluted  sew^age  or  effluent,  —  the  water  used 
for  dilution  furnishing  the  necessary  oxygen,  —  is  tested  for 
dissolved  oxygen.  A  sample  is  then  incubated  in  a  closed  bottle 
for  five  days  at  20°  C.  and  the  dissolved  oxygen  again  deter- 
mined. The  difference  represents  the  oxygen  absorbed,  and 
should  not  be  greater  than  20  parts  per  million. 

Procedure.  —  If  the  water  is  from  a  stream  or  lake,  fill  com- 
pletely two  300-c.c.  calibrated  glass-stoppered  bottles.  Insert 
the  stoppers,  taking  care  that  no  air  bubbles  are  enclosed.  If  a 
sewage  or  effluent  is  being  tested,  make  dilutions  with  tap  water 
as  follows: 

Raw  sewage.     Dilute  6  c.c.  to  600  c.c. 
Settling  tank  effluents.     Dilute  12  c.c.  to  600  c.c. 
Filter  effluents.     Dilute  120  c.c.  to  600  c.c. 
Fill  two  calibrated  bottles  as  just  described. 

Make  a  dissolved  oxygen  test  on  one  bottle,  following  the 
directions  as  given  for  putrescibility  tests.  Set  the  other  bottle 
in  a  20°  incubator  and  let  stand  for  five  days.  Then  determine 
the  dissolved  oxygen  agam.  Calculate  the  results  in  terms  of 
oxygen  absorbed  by  the  original  sample  of  water,  sewage  or 
effluent. 

Determination  of  the  Color.  —  The  amount  of  color  is  gen- 
erally determined  by  direct  comparison  of  the  water  with  some 
definite  standard  of  color.     Various  standards  have  been  pro- 

*  Eng.  Rcc,  1913,  68,  pp.  315  and  453;  Am.  J.  Pub.  Health,  1914.  4,  p.  2.^1. 


Io6  AIR,  WATER,  AND   FOOD 

posed,  the  objection  to  most  of  them  being  that  they  are  not 
sufficiently  general  in  their  application,  being  adapted  only  for 
the  color  of  some  particular  class  of  waters. 

The  standard  in  most  general  use  is  the  platinum  standard. 
The  comparisons  of  the  water  with  the  color  standards  are  most 
readily  made  in  50-c.c.  Nessler  tubes.  According  to  this  scale, 
the  color  of  a  water  is  the  amount  of  platinum  in  parts  per 
million,  which,  together  with  enough  cobalt  to  match  the  tint, 
must  be  dissolved  in  distilled  water  to  produce  an  equal  color. 
In  practice,  a  standard  having  a  color  of  500  is  prepared  by  dis- 
solving 1.246  grams  of  potassium  platinic  chloride  (equivalent 
to  0.5  gram  platinum),  i.o  gram  of  cobalt  chloride  (equivalent 
to  0.25  gram  cobalt),  and  100  c.c.  of  strong  hydrochloric  acid  in 
distilled  water  and  diluting  to  one  liter. 

Dilute  standards  for  use  are  made  by  diluting  varying  amounts 
of  this  standard  to  50  c.c.  with  distilled  water.  Thus,  by  dilut- 
ing one  c.c,  two  c.c,  and  three  c.c.  each  to  50  c.c,  colors  of  10, 
20,  and  30  are  obtained.  It  is  claimed  that  the  platinum 
standards  are  permanent  if  protected  from  the  dust,  but  in  this 
laboratory  it  has  been  found  necessary  to  replace  them  about 
once  a  month. 

Determination  of  the  Odor.  —  Cold.  —  Shake  violently  the 
sample  in  one  of  the  large  collecting-bottles  when  it  is  about 
half  or  two-thirds  full,  then  remove  the  stopper  and  quickly 
put  the  nose  to  the  mouth  of  the  bottle.  Note  the  character 
and  degree  of  intensity  of  the  odor,  if  any.  An  odor  can  be  often 
detected  in  this  way  which  would  be  entirely  inappreciable  if 
the  water  were  poured  into  a  tumbler. 

Hot.  —  Pour  into  a  plain  beaker  about  five  inches  high  enough 
water  to  one-third  fill  it.  Cover  the  beaker  with  a  well-fitting 
watch-glass  and  place  it  on  an  iron  plate  which  has  been  pre- 
viously heated,  so  that  the  water  shall  quickly  come  to  a  boil. 
When  the  air  bubbles  have  all  been  driven  off  and  the  water  is 
about  to  boil,  take  the  beaker  from  the  plate  and  allow  it  to  cool 
for  about  five  minutes.  Then  shake  it  with  a  rotary  movement, 
slip  the  watch-glass  to  one  side  and  put  the  nose  into  the  beaker. 


WATER:    ANALYTICAL  METHODS  107 

Note  the  odor  as  before.  The  odor  may  or  may  not  be  the  same 
as  that  of  the  water  when  cold;  it  can  be  perceived,  as  a  rule, 
for  only  an  instant. 

Notes.  —  It  is  inevitable  that  a  certain  personal  equation 
should  influence  this  test.  Each  laboratory  will  have  its  own 
standards  for  routine  work,  but  a  certain  familiarity  with  the 
more  common  odors  will  tend  to  allay  public  anxiety  and  to  aid 
in  a  more  watchful  habit  on  the  part  of  consumers.  Good 
ground  waters  do  not  give  distinct  odors  unless  they  are  derived 
from  clayey  soil,  but  the  odor  often  betrays  a  contaminated 
well.  Surface-waters  will  nearly  always  yield  a  characteristic 
odor.  This  odor  may  be  due  to  the  organic  matter  contained 
in  the  water,  or  to  the  presence  of  minute  plants  or  animal 
organisms. 

Among  the  odors  which  are  frequently  met  are  "earthy," 
"vegetable,"  "musty,"  "mouldy,"  "disagreeable,"  and  "offen- 
sive." The  "earthy"  odor  is  that  of  freshly  turned  clayey  soil. 
"Vegetable"  is  the  odor  of  many  normal  colored  surface-waters; 
it  may  be  described  as  swampy  or  marshy,  pond-like,  and  is 
often  strengthened  by  heating.  "Musty"  can  be  likened  to 
the  odor  of  damp  straw  from  stables;  it  is  fairly  characteristic 
of  sewage  contamination,  and  by  the  trained  observer  is  dis- 
tinctly distinguishable  from  the  mouldy  odor.  "Mouldy"  is 
the  odor  of  upturned  garden  or  forest  mould,  or  of  a  moist  hot- 
house; it  is  somewhat  alHed  to  the  earthy  odor.  "Disagree- 
able" is  a  term  which  is  capable  of  wide  variation  among  different 
observers.  It  may  include  certain  characteristic  odors  which 
are  peculiar  to  the  growth  or  decay  of  certain  organisms,  as  the 
"pigpen"  odor  of  AnahcBna,  the  "fishy"  or  "cucumber"  odor 
of  Synura,  etc.  The  term  "offensive"  is  generally  reserved  for 
the  sewages.  These  terms  can  be  taken  only  as  broad  illustra- 
tions of  the  character  of  the  particular  odor,  since  the  odor  will 
very  likely  be  described  by  different  persons  in  different  ways, 
and  each  laboratory  will  have  its  own  characterization.  The 
odor  which  often  accompanies  an  abundant  development  of 
diatoms  is  a  good  illustration  of  this.     It  will  be  called  bv  various 


Io8  AIR,   WATER,   AND   FOOD 

inexperienced  observers  offensive,  rotten,  fishy,  geranium-like, 
aromatic,  in  one  and  the  same  sample  of  water. 

The  terms  generally  used  to  signify  the  degree  of  intensity 
of  the  odor  are  "very  faint,"  "faint,"  "distinct,"  and  "decided." 
The  exact  value  to  be  placed  upon  each  of  these  terms  will,  as  a 
matter  of  course,  vary  with  the  individual  analyst,  but  in  a 
general  way,  it  may  be  said  that  the  "very  faint"  odor  is  one 
that  would  not  be  detected  except  by  the  trained  observer;  the 
"faint"  odor  would  be  recognized  by  the  ordinary  consumer  if 
his  attention  were  called  to  it;  the  "distinct"  odor  is  one  that 
would  be  readily  noticed  by  the  average  consumer,  but  would 
not  interfere  with  the  use  of  the  water;  while  the  "decided" 
odor ^ is  one  which  would,  in  all  probability,  render  the  use  of 
the  water  unpleasant. 

Determination  of  the  Turbidity  and  Sediment.  —  The  sus- 
pended matter  remaining  in  the  water  after  it  has  rested  quietly 
in  the  collecting-bottle  for  twelve  hours,  or  more,  is  called  its 
turbidity,  and  that  which  has  settled  to  the  bottom  of  the  bottle, 
its  sediment. 

Good  ground  waters  are  often  entirely  free  from  turbidity 
and  sediment,  the  suspended  matters  having  been  filtered  out 
during  the  subterranean  passage  of  the  water,  but  this  is  rarely 
true  of  surface-waters.  The  turbidity  is  various  in  character 
and  amount,  sometimes  milky  from  clay  or  ferrous  iron  in  solu- 
tion ;  usually  it  consists  of  fine  particles,  generally  living  algae  or 
infusoria.  These  often  collect  on  the  side  toward  or  from  the 
light,  and  a  practiced  eye  can,  not  infrequently,  recognize  their 
forms.  Some  of  the  lower  animal  forms  can  also  be  seen  by  the 
naked  eye,  and  the  larger  Entomostraca  are  quite  noticeable 
in  many  waters. 

The  sediment  may  be  earthy  or  flocculent;  in  the  latter  case 
it  is  generally  debris  of  organic  matter  of  various  kinds.  The 
degree  of  turbidity  is  expressed  by  the  terms  "very  sHght," 
"slight,"  "distinct,"  and  "decided,"  and  the  degree  of  sedi- 
ment by  "very  slight,"  "slight,"  "considerable,"  and  "heavy." 
These  determinations,  again,  are  of  value  only  to  the  routine 


WATER:    ANALYTICAL  METHODS 


109 


worker,  and  for  him  there  are  various  methods  in  use.  The 
papers  of  Pannclce  and  Ellms  *  and  of  WTiipple  and  Jackson  t 
should  be  consulted  for  a  description  of  these. 

Sewage  Analysis.^  —  The  methods  for  the  analysis  of  sew- 
ages and  sewage  effluents  are  the  same  as  those  described  for 
water.  The  main  difference  is  in  the  quantities  used  for  the 
various  determinations.  In  most  cases,  this  has  been  noted  in 
connection  with  the  analysis.  Great  care  should  also  be  exer- 
cised in  taking  samples  from  a  bottle  as  the  large  amount  of 
suspended  matter  makes  it  more  difficult  to  obtain  a  represent- 
ative portion.  Special  attention  is  called  to  the  putrescibility 
test  (p.  105)  for  effluents,  as  stability  is  the  main  desire  in  treat- 
ing a  large  proportion  of  sewages. 

Biological  Examination.  —  Since  a  large  number  of,  if  not  all, 
diseases  are  caused  by  living  organisms,  it  would  seem  most 
desirable  in  examining  a  water  supply  if  the  specific  organisms 
causing  water-borne  diseases  could  be  looked  for,  and,  if  present, 
isolated.  However,  it  is  quite  impossible  to  do  this  in  the  great 
majority  of  cases,  and  so  in  bacteriological  work,  just  as  in 
chemical  analysis,  certain  indications  of  the  presence  of  sewage 
are  sought  for,  and  if  these  indications  are  positive,  the  water 
is  condemned.  In  a  bacteriological  examination,  the  most 
important  index  of  the  presence  of  sewage  is  finding  B.  coU  in 
quantities  as  great  as  one  in  each  cubic  centimeter.  This 
organism  is  a  normal  inhabitant  of  the  intestines  of  man  and 
the  higher  animals  and  is  present  in  large  numbers  in  human 
and  animal  excreta.  Its  presence,  therefore,  in  water  shows 
the  presence  also  of  sewage.  For  a  discussion  of  water  bacteri- 
ology and  methods  of  analysis  the  reader  is  referred  to  another 
book.§ 

The  close  relation  of  the  odor  to  the  living  flora  and  fauna  of 


*  Tech.  Quart.,  12,  1899,  p.  145. 
t  Ihid.,  p.  283. 

X  See  Fowler  "Sewage  Works  .Analyses,"  John  \\ilcy  &  Sons,  1902. 
§  Prescott   and   Winslow,   "Elements  of  Water   Bacteriology,"   3rd    edition. 
John  Wiley  &  Sons,  19 13. 


no  AIR,  WATER,  AND  FOOD 

the  water  makes  it  desirable  that  the  chemist  shall  be  able  to 
recognize  the  more  common  forms  of  water  plants  and  animals, 
even  if  he  make  no  pretensions  to  a  knowledge  of  cryptogamic 
botany  or  of  zoology.  Therefore,  a  microscope  and  a  concen- 
tration apparatus  should  be  in  every  water-laboratory.  A  full 
description  will  be  found  elsewhere.* 

*  Whipple,  "The  Microscopy  of  Drinking  Water,"  3rd  edition,  John  Wiley 
&  Sons,  IQ14. 


CHAPTER  VII 

FOOD   IN   RELATION   TO   HUMAN   LIFE:     COMPOSITION, 
SOURCES,   DIETARIES 

Life  itself  is  conditioned  on  the  food-supply.  WTiolesome 
food  is  a  necessity  for  productive  life.  IMan  can  and  does  exist 
on  very  unsuitable,  even  more  or  less  poisonous,  food,  but  it  is 
merely  existence  and  not  effective  life.  This  is  true  not  onl}-  of 
the  wage-earner,  but  of  the  business-man,  the  professional  man, 
the  scholar.  To  be  well,  to  be  able  to  do  a  day's  work,  is  man's 
birthright.  Nevertheless,  a  too  large  proportion  of  the  American 
people  sells  this  most  valuable  possession  for  a  mess  of  pottage 
which  pleases  the  palate  for  three  minutes  and  weights  the  diges- 
tive organs  for  three  hours.  With  the  products  of  the  world  ex- 
posed in  our  markets,  the  restraints  of  a  restricted  choice,  as  well 
as  inherited  instincts  or  traditions,  lose  their  force.  The  buyer, 
unless  he  has  actual  knowledge  to  guide  him,  is  swayed  b\-  the 
caprices  of  the  moment  or  the  condition  of  his  purse,  and  often 
fails  to  secure  adequate  return  in  nutritive  value  for  the  money 
paid.  The  fact  that  so  much  manipulated  material  is  put  upon 
the  market  renders  this  choice  of  food  doubly  difficult,  since  the 
appearance  of  the  original  article  is  often  entirely  lost,  and  to 
city-bred  buyers  even  the  natural  product  conveys  little  idea  of 
its  money  value.  It  is  now  even  more  necessary  that  an  elemen- 
tary knowledge  of  the  proximate  composition  and  food  value  of 
the  more  common  edible  substances  should  be  recognized  as  an 
essential  part  of  education. 

Food:  Definition  and  Uses.  —  Food  is  that  which  builds  up  the 
body  and  furnishes  energy  for  its  activities:  that  which  brings 
within  reach  of  the  living  cells  which  fonn  the  tissues  the  elements 
which  they  need  for  life  and  growth.  Only  such  available  sub- 
stances can  be  called  food,  no  matter  what  their  chemical  compo- 


112  AIR,   WATER,   AND   FOOD 

sition  may  be.  Soft  coal  contains  carbon  and  hydrogen  and  is 
food  for  the  furnace,  but  is  not  available  for  the  animal  body. 

This  food  which  is  taken  into  the  body  is  used  in  various  ways. 
It  forms  and  builds  up  new  tissues,  besides  repairing  and  making 
good  the  waste  of  tissues  due  to  bodily  activity ;  it  is  stored  up  in 
the  body  to  meet  a  future  demand;  it  supplies  the  needed  heat 
by  the  transformation  of  its  stored  up  or  potential  energy  into 
the  muscular  energy  required  by  the  body;  it  may  be  used  to 
protect  the  tissues  of  the  body  from  being  themselves  consumed 
as  food. 

Composition  of  Food.  —  We  determine  what  chemical  elements 
enter  into  the  composition  of  the  body  by  an  analysis  of  the  vari- 
ous organs  and  tissues.  We  learn  what  combinations  of  these  ele- 
ments serve  as  food  by  determining  those  present  in  mother's  milk 
and  in  foodstuffs  which  experience  has  proved  to  furnish  perfect 
nutrition.  From  these  studies  it  is  apparent  that  about  fifteen 
chemical  elements  are  constant  constituents  of  the  human  body; 
that  about  a  thousand  natural  products  are  known  to  have  food 
value;  that  of  these,  one  hundred  are  of  world-wide  importance 
(see  table,  page  ii8),  and  that  ten  of  them  form  nine-tenths  of 
the  food  of  the  world. 

The  composition  of  food,  as  shown  by  chemical  analysis,  is 
not,  however,  the  only  factor  that  must  be  known  to  determine  its 
value.  The  digestibility  of  the  material  must  be  taken  into  ac- 
count as  well.  "We  live  not  upon  what  we  eat,  but  upon  what 
we  digest."  It  is  more  important  to  know  the  amount  of  availa- 
ble nutrients  than  the  amount  of  total  nutrients. 

Food  Principles.  —  While  the  foodstuffs  present  great  variety, 
the  food  principles  may  be  grouped  under  four  headings;  viz., 
nitrogenous  substances  or  proteids,  fats,  carbohydrates,  and 
mineral  salts.  Each  group  contains  many  members  with  minor 
but  often  essential  differences.  To  make  these  substances 
available,  there  is  needed  an  ample  supply  of  air  and  of  water, 
—  of  water  for  solution  and  circulation,  of  air  for  the  oxygen 
needed  to  liberate  the  stored  energy  of  the  food  in  the  place 
where  it  will  accomplish  its  purpose. 


FOOD   IN  RELATION  TO  HUMAN  LIFE  113 

Nitrogenous  Substances.  —  Since,  in  some  way  as  yet  un- 
known to  us,  nitrogen  is  essential  to  living  matter,  such  sub- 
stances as  contain  this  element  in  an  available  form  arc  of  the 
first  importance.  Some,  as  albumen,  are  so  closely  allied  to 
human  protoplasm  that  probably  they  need  only  to  be  dissolved 
to  be  at  once  assimilated.  Others,  as  gluten  and  similar  vege- 
table products,  undergo  a  greater  change;  while  still  others, 
as  gelatine,  have  a  less  profound  but  marked  effect  in  protecting 
the  tissues  from  waste. 

The"  enzymes,  "ferments,"  in  part,  of  the  older  nomencla- 
ture, are  also  highly  nitrogenous  substances  present  in  some 
form  in  nearly  all  foodstuffs  of  natural  origin.  The  nearer  the 
composition  of  the  food  approaches  that  of  the  protoplasmic 
proteid,  presumably  the  greater  its  food  value,  since  each  cleav- 
age, each  hydrolysis,  each  step  in  the  breaking  down  of  the 
highly  complex  molecule,  consisting  of  hundreds  of  atoms,  is 
supposed  to  liberate  the  stored  energy.  Therefore,  it  is  not  a 
matter  of  indifference  in  what  form  this  essential  is  taken.  So 
little  is  known,  however,  with  scientific  accuracy  that  students 
will  find  a  fruitful  field  of  research  along  these  lines  of  inves- 
tigation. Also  together  with  this  element,  nitrogen,  go  others, 
in  small  quantity  to  be  sure,  but  evidently  of  great  value.  Such 
are  sulphur,  iron,  phosphorus.  One  difference  between  the 
several  groups  of  proteids  is  seen  in  this  combination  with  the 
metallic  elements  which  seems  to  carry  with  it  certain  effects. 
Until  greater  progress  has  been  made  in  determining  the 
availability  in  the  organism  of  the  various  known  substances, 
we  must  be  content  with  a  wide  margin  in  the  calculated  quan- 
tities necessary  for  the  daily  efficiency,  except  in  the  very  few 
instances  of  nearly  pure  substances,  as  white  of  egg.  It  is 
evident,  also,  that  the  manner  of  preparation  and  the  kind  of 
mixtures  used  in  food  will  affect  most  profoundly  so  unstable 
and  complex  a  class  of  substances.  One  thing  is  certain,  that 
the  body  cannot  take  nitrogen  from  that  which  does  not  contain 
it.  Therefore,  a  certain  quantity  of  highly  nitrogenous  food 
should  form  a  portion  of  the  daily  supply.     It  is  usually  held 


114  AIR,  WATER,  AND   FOOD 

that  the  body  seems  to  be  sufficiently  nourished  when  the  food 
contains  an  amount  of  digestible  proteid  equivalent  to  about  loo 
grams  of  dry  albumen  per  day  for  the  average  adult,  although 
recent  work  has  shown  that  this  figure  is  probably  too  high. 
An  excess  appears  to  have  a  stimulating  effect  and  overloads 
the  system  with  the  waste,  since  the  end-products  are  not  purely 
mineralized  substances,  as  are  carbon  dioxide  and  water  from 
the  carbohydrates,  but  are  compounds  of  an  organic  nature, 
as  creatin,  urea,  and  uric  acid,  which  have  deleterious  effects 
when  accumulated  in  the  system.  A  deficiency  of  nitrogen  is 
made  good,  to  a  limited  extent,  by  the  protective  agency  of  the 
other  foodstuffs  which  offer  themselves  for  all  the  offices  except 
the  final  one  of  tissue-building. 

Fats.  —  For  this  protective  action,  as  well  as  for  many  other 
purposes,  the  fats  are  most  valuable,  and  if  they  occur  in  about 
the  same  proportion  as  do  the  nitrogenous  elements,  the  needs 
of  the  organism  seem  to  be  well  met.  Thus,  in  mother's  milk, 
in  eggs,  and  in  meat  from  active  animals  these  two  are  in  nearly 
equal  proportions,  while  in  the  cereals  the  fat  is  less;  in  nuts 
and  in  meat  from  fattened  animals,  as  a  rule,  it  is  higher  than 
the  nitrogen.  Little  is  known  as  to  the  varying  food  value  of 
these  fats  from  different  sources.  Certain  physical  conditions 
of  solidity,  melting-point,  etc.,  seem  to  have  more  influence 
than  mere  chemical  composition.  Whatever  the  source,  it  is 
certain  that  the  stored-up  energy  which  is  to  serve  the  organism 
in  cases  of  loss  of  income  from  any  cause  is  in  the  form  of  fat, 
a  form  which  is  not  subject  to  the  action  of  agents  which  so 
readily  decompose  proteids  and  carbohydrates  and  yet  is  readily 
converted  into  available  food  whenever  called  for.  That  it  is 
not  absolutely  necessary  that  the  food  should  contain  fat  as 
such  seems  to  be  proved  by  experiment,  but  from  the  fact  that 
nearly  all  natural  food-substances  do  contain  it,  and  that  it 
appears  to  be  more  economical  of  human  energy  to  take  it  from 
these  foods  than  to  manufacture  it  from  the  proteids  and  carbo- 
hydrates, we  may  safely  assume  fat  to  be  an  essential  of  the 
human  dietary. 


FOOD   IX  RELATION  TO   HUMAN  LIFE  115 

That  the  equality  in  amount  of  fat  with  nitrogenous  com- 
pounds is  not  essential  is  proved  by  the  fact  that  the  strong 
draft  animals,  as  horses  and  oxen,  take  food  in  which  the  per 
cent  of  fat  is  not  more  than  half  as  much  as  of  proteid;  never- 
theless, it  is  present  in  the  food  of  all  animals  and  doubtless, 
in  its  turn,  is  protected  by  an  excess  of  the  third  class  of  food- 
stuffs, the  carbohydrates,  characteristic  of  the  vegetable  king- 
dom —  a  class  which  in  the  final  decomposition,  yields  clean 
volatile  products,  water  and  carbon  dioxide,  and  which,  there- 
fore, do  not  clog  the  system  so  readily  as  do  urea  and  other 
wastes. 

Carbohydrates.  —  The  number  of  more  or  less  well-defined 
substances  under  this  head  is  legion:  starches  from  scores  of 
plants,  sugars  from  as  many  more,  gums,  pectins,  and  dextrins, 
all  with  a  certain  food  value,  dependent  probably  upon  the 
utilization  of  the  various  mixtures  with  which  they  are  taken 
into  the  alimentary  canal.  These  foodstuffs  are  very  liable  to 
*' fermentation,"  that  is,  to  an  acid  decomposition  which  pre- 
vents their  absorption  by  the  delicate  lining  of  the  walls  of  the 
intestines  and  which  causes  digestive  disturbance.  The  sugars, 
which  are  very  soluble,  and,  therefore,  liable  to  be  present  in 
excess,  are  especially  subject  to  this  change.  This  class  of 
food-substances  is  found  in  the  diet  of  civilized  man,  free  to 
choose,  in  an  amount  about  equal  to  the  sum  of  the  other  two 
classes,  with  a  tendency  to  less  rather  than  more.  It  may  be 
said  that  sugar  and  fat  increase  over  starch  in  the  diet  of  a  people 
of  unrestricted  choice,  but  it  is  not  certain  that  the  qualities  of 
body  which  make  for  hardihood  and  resistance  to  disease  are 
correspondingly  increased.  There  is,  indeed,  much  evidence 
to  show  that  power  of  digesting  vegetable  foods  indicates  a 
general  well-being  of  body  conducive  to  long  life.  A  ready 
adaptation  renders  possible  the  changes  of  habitat  required  by 
civilization.  Unless  one  is  to  be  confined  to  a  narrow  range,  it 
is  wise  to  cultivate  a  strength  of  digestion  as  well  as  a  strength  of 
muscle,  and  for  the  best  brain  power  we  believe  it  to  be  more 
essential. 


Il6  AIR,   WATER,   AND   FOOD 

Mineral  Salts.  —  The  fourth  class,  mmeral  salts,  comes  into 
the  food  largely  from  the  vegetable  substances  eaten,  for  in 
these  the  union  is  an  organic  one  readily  assimilated.  As  we 
have  seen,  certain  elements  go  with  the  nitrogenous  portion, 
as,  for  example,  in  gluten  and  its  congeners  are  found  sulphur 
and  phosphorus.  Potassium,  found  in  barley,  is  a  constant 
constituent  of  protoplasm,  while  sodium  is  found  in  blood- 
serum.  A  lack  of  vegetable  foods  seems  to  impoverish  the 
blood-corpuscles.  For  children,  a  deficiency  in  lime  causes 
serious  disease.  Sugar,  olive-oil,  corn-starch  and  other  prepared 
food-substances  cannot  take  the  place  of  asparagus,  cabbage, 
carrots,  etc. 

To  sum  up  briefly,  then,  we  may  say  that  the  protein  or  nitrog- 
enous portion  of  the  food  forms  tissue,  such  as  muscle,  sinew  and 
fat,  and  furnishes  energy  in  the  form  of  heat  and  muscular 
strength;  the  fats  build  up  fatty  tissue,  but  not  muscle,  and 
supply  heat;  the  carbohydrates  are  changed  into  fat  and  supply 
heat.  Another  important  use  of  the  nutrients  is  to  protect 
each  other  from  being  used  in  the  body.  The  carbohydrates, 
especially,  in  this  way  protect  the  protein,  including  muscle, 
etc.,  from  consumption. 

Change  in  Composition  Due  to  Cooking.  —  The  composition  of 
cooked  foods  is  in  general  not  the  same  as  the  raw  material  on  ac- 
count principally  of  chemical  and  physical  changes  brought  about 
by  the  heat  employed  in  the  cooking  process.  The  total  nutri- 
ents, calculated  on  a  water-free  basis,  may  be  practically  the 
same,  but  the  structure  is  often  quite  different. 

Starch  is  hydrolyzed  and  rendered  soluble  by  heating  in  the 
presence  of  moisture,  and  at  higher  temperatures  it  may  be 
converted  into  the  brown,  soluble  dextrin.  The  sugars  are 
changed,  being,  in  the  case  of  sucrose,  partly  converted  into 
other  forms,  such  as  invert  sugar,  by  the  heating,  with  the  help 
of  the  organic  acids  present  in  many  foods.  Some  of  the  proteids 
tend  to  become  less  soluble  through  heating  and  at  higher  tem- 
peratures may  be  even  partly  decomposed  with  possible  loss  of 
food  value. 


FOOD   IN  RELATION   TO  HUMAN  LIFE  117 

Eeai  of  Combustion.  —  Until  a  more  definite  knowledge  of  the 
processes  of  metabolism  (the  transformations  of  matter  and 
energy  in  the  animal  organism)  is  obtained  the  potential  energy 
of  food  is  calculated  in  terms  of  mechanical  work  —  expressed 
in  heat-units  or  calories. 

One  calorie  is  the  amount  of  heat  rcc^uired  to  raise  the  tempera- 
ture of  one  gram  of  water  one  degree  centigrade.  A  gram  of  fat, 
as  actually  digested  and  oxidized  in  the  body,  affords  enough 
heat  to  raise  the  temperature  of  about  9000  grams  of  water  one 
degree.  In  like  manner  a  gram  of  protein  has  an  energ>'-pro- 
ducing  power  expressed  in  calories  of  about  4000,  and  for  carbo- 
hydrates the  average  value  is  also  4000. 

Allowance  is  made  in  these  figures  for  the  fact  that  to  digest 
completely  any  part  of  our  food  results  in  a  decrease  of  the 
amount  of  energy  to  be  derived  from  it,  and  this  affects  the 
protein  more  than  it  does  the  other  two.  It  is  probably  true 
that  under  favorable  conditions  the  fat  and  carbohydrates 
can  be  completely  utilized  in  the  body  and  consequently  their 
energy-producing  power  can  be  correctly  estimated  from  their 
heat-producing  power  outside  the  body.  In  the  case  of  pro- 
tein, however,  the  digestion  within  the  body  is  never  so  com- 
plete as  to  furnish  all  the  energy  that  would  be  obtained  by  a 
complete  combustion  of  these  nitrogenous  materials  outside  of 
the  body. 

The  fact  remains,  however,  that  all  experiments  yet  made  go 
to  show  that  within  practical  limits  we  are  safe  in  using  the  heat 
of  combustion  (expressed  in  calories)  of  any  food-substance  as  a 
controlling  measure  of  food  values. 

Nutritive  Ratio.  —  The  requisite  number  of  calories  must,  how- 
ever, be  obtained  by  the  utilization  of  such  substances  as  contain 
all  the  elements  needed  by  the  body,  and  in  such  ratio  as  has  been 
found  available  for  the  balance  of  nutrition.  In  carrying  on  its 
multifarious  activities  the  body  loses  about  20  grams  of  nitrogen 
per  day,  which  must  be  replaced  by  the  same  element  in  the  food 
taken.  Thus  while  the  requisite  number  of  calories  may  be  fur- 
nished by  fat  or  starch,  these  substances  alone  will  not  suffice  for 


ii8 


AIR,   WATER,  AND   FOOD 


COMPOSITION  OF  SOME  COMMON   FOOD-MATERIALS  AS  PURCHASED 

I.   Fuel  Value  3000-4000  Calories  *  per  Pound 


Food-material. 


Butter 

Lard  (refined). .  . . 
Oleomargarine.  .  . 

Salt  fat  pork 

Suet 

Walnuts  (shelled). 


Refuse. 


Per  cent. 


Water. 


Per  cent. 

II. o 

9  5 
0.3  to  12.2 
4.3  to  21.9 

2.5 


Nitroge- 
nous 
Substances 


Per  cent. 


0.2  to  5.0 

I.I  to7S 

16  6 


Fat. 


Per  cent. 
85.0 
100.00 
83.0 
80 . 3  to  94 . 1 
70.7  to  94. S 
63  4 


II.  Fuel  Value  2000-3000  Calories  per  Pound 


Bacon 

Cheese  (American  pale). 

Chocolate 

Doughnuts 

Mutton  flank  (fat) 

Peanut  butter 

Sausage  (farmer) 


8.7 


3.9 


18.4 

31.6 

I 

5  to  10 

3 

II 

Ot0  25 

28.9 
2.1 
22.2 

8 

9  5 
28.8 
12.5  to  13.4 
S.I  to  76 
10.7 
29  3 
27.9 


59.4 

35  9 
47.1  to  50.2 
16.4  to  25.7 

59.8 

46. S 

40.4 


Carbo- 
hydrates. 


Per  cent. 


0.3 
26.8  to  33-8 
45-8  1063.2 


III.   Fuel  Value  11:00-2000  Calories  per  Pound 


Barley  (pearled ) 

Beans  (dried) 

Cake  average  (except  fruit) . . . 

Candy 

Cheese  (.NIeuchatel) 

Corn  meal 

Corn -starch 

Crackers  (average) 

Fat  meats 

Gelatin 

Ham  (smoked,  medium  fat). 
Infants'  and  invalids'  foods.. 

Macaroni 

Oats 

Peanuts 

Peas  (dried) 

Pop-corn 

Rice 

Rye  flour 

Sugar  (granulated) 

Wheat  (entire)  flour 

Wheat  flour  (white  bakers'). 

Wheat  (shredded) 

Zwieback 


11. 7 

4.5  to  28.4 


9.8  to  12.9 

9.6  to  15  5 

19.9 

4.0 

42.7  to  57-2 

8.8  to  17.9 
10. o 

6.8 

38.3 

13.6 

27.3  to  42.5 

2.4  to  12.3 

7.0  to  12.3 

7.8 
6.9 

6.9  to  15.0 
4  3 

9.1  to  14.0 
II. 9  to  13.6 


6.4  to  13. 1 
10. I  to  13.3 
7.2  to  10  7 
5.0  to  7-7 
*  Including  fibre 


7.0  to  10. 1 

19.9  to  26.6 

6.3 

15. 1  to  22.3 
6.7  to  II. 6 

10.7 
13  0 
84.2 

10.2  to  21.9 
2.0  to  22.5 
7.9  to  16.6 

16. S 

19.5 
20.4  to  28.0 

10.7 
59  to  II. 3 
4.9  to    8.8 

12.2  to  14.6 

10.3  to  14.9 
9.6  to  II. 4 
8.6  to  II. 7 


o.7to  i.s 

1.4  to3.l 

9.0 

22.3  to  32. 5 

l.otos.3 

8.8 

36.8 

01 

24.S  to39.9 

0.3  to  10.9 

0.0  to  4.9 

7  3 

29.1 

0.8  to  1.3 

50 

o.i  to  0.7 

0.2  to  1.3 

I.S  to  2.1 

1.9  to  2.0 

1.3  to  1.6 

8.1  to  II. 3 

77-3  to  78.1* 
57-2  to  63.5* 

63.3 

96.0 
0.2  to  2.9 
68.4  to  80.6* 

90.0* 

71  9* 


66 . 9  to  89 . 4 

67.2  to  78.4* 
66.  s* 
18. S 

58.0  to  67.4* 
78.7 

75. 4  to  81.9* 
77.6  to  80.2* 

100 

69.5  to  770* 

70.3  to  75  S 

75.0  to  79-7* 

72.1  to  74.2 


IV.  Fuel  Value  1000-15000  Calories  per  Pound 


Apples  (dried) 

Bread  (white) 

Corn-bread 

Dates 

Figs 

Fresh  pork  (ribs  and  shoulder). 
Medium  fat  mutton  and  beef. . 

Mince-meat  (commercial) 

Mince-meat  (home-made) 

Pies 

Prunes  (dried ) 

Raisins 

Sandwiches 

Sardines  (canned) 

Salt  mackerel 


159  to  20.3 
14.4  to  27.8 


15.0 
10. o 


5.0 
22.9 


8.6  to 

47.4  1 

35.3 

28.4  to  48.0 

13.8 

II. 6  to  25. 0 

40.1  to  43.6 

38.0  to  44-9 

27.7 

54 

4 

44 

9 

19 

0 

13 

I 

44 

9 

S3 

6 

32 

5 

1 . 2  to  2 .  s 
9.2 

6.5  to  10. 1 
19 

2 . 6  to  5 . 7 
13.7  to  14.5 
II. 4  to  12.9 

6.7 
4 


•  One  Calorie  equals  looo  calories. 


FOOD   IN  RELATION   TO   HUMAN   LIFE 


119 


COMPOSITION   OF  SOME  COMMON   FOOD   MATERIALS.  -  Con/.n««/ 

V.   Fuel  Value  500-icxx)  Calories  per  Pound 


Food-material. 


Beef  (round) 

Beef  (sirloin  steak). 
Chicken  (fowls) . . . . 

Cream 

Eggs 

Herring  (smoked). . 

Meats  (lean) 

Olives 

Salmon  (fresh) 

Salmon  (canned)... 
Tapioca  pudding.  .  . 

Tongue    (beef) 

Turkey 

Veal  (breast) 


Refuse. 


Per  cent. 

8.5 

12.8 

18.0  to  42.7 


II. 2 

44  4 
0.5  to  II. 3 

19.0 
23.8  to  35.1 
1 1. 7  to  16.9 


9.2  to  55-3 
17.1  to  32.4 
15.7  to  25.4 


Water. 

Per  cent. 

62. s 

54-0 

38.31053.7 

74.0 

65  5 

19  2 

59.9  to  69.2 

52.4 

45  otosi  2 

54  6  to  58 . 2 

52.0  to  71.6 

32.4  to  69.2 

41. 1  to  44-7 

48.51055-7 

Nitroge- 
nous 
Substances 


Per  cent. 
19.2 
16. 5 

11. 5  to  16.0 

2.5 

II. 9 

20.5 

18. 1  to  21.4 
14 

12.6  to  15- o 
18.6  to  20.2 

2.8  to  4.2 
7.8  to  20.2 
15.8  to  16.8 

14.2  to  16.9 


Fat. 


Per  cent 
9.2 
16. 1 
6.9  to  21.5 
18. 5 
9  3 
8.8 
7.8  to  14.2 

21.0 
6.6to    9.5 
5.6to    9.8 

2.3  to  4  8 
0.7  to  IS. 3 
5.91025.5 

9.4  to  12.8 


VI.   Fuel  Value  4oo-5cx3  Calories  per  Pound 


Beans  (canned  red  kidney) . 

Calf's-foot  jelly 

Salt  cod  (boneless) 

Succotash  (canned) 

Sweet  potatoes 


1.6 


72.7 
77.6 
54.8 
71.4  to  79.9 
55-2 


7.0 

4.3 

27.7 

2.9  to  4.4 

1.4 


0.3 

0.7  to  1.7 

0.6 


VII.   Fuel  Value  300-400  Calories  per  Pound 


Bananas 

Butter  beans. 
Fish  (fresh).. 

Grapes 

Hash 

Milk 

Potatoes 


35  o  I  48.9 
50.0  I  29.4 
25.2  to  46.0  46.1  to  49. 1 
S8.o 
80.3 
87.0 
62.6 


08 
4.7 
II. 9  to  12.0 
1.0 
6.0 
3  3 


0.4 
0.3 
1.8  to5.9 
1.2 
19 
4.0 


Carbo- 
hydrates. 


Per  cent. 

4-5 

3  5 
21.9  to  ;^.i 


18.5 
17  4 


14.9  to  22.4 
21.9 


14  3 
14  6 


14.4 
9  4 

SO 
14.7 


VIII.   Fuel  Value  200-300  Calories  per  Pound 


Apples 

Chicken  (broilers). 

Cranberries 

Onions 

Oysters  (.solid). . . . 

Parsnips 

Pears 


25.0 
31.4  to  55. 


20.0 
10.0 


63.3 
44-6  to  52.4 
87.6  to  89.5 

78.9 
82.2  to  92.4 

66.4 

76.2 


0.3 
9.0  to  IS. 7 
0.4  to  0.5 

1.4 
4  5  to7  3 

13 

OS 


0.3 
I.I  to  1.8 
0.4  to  0.9 

0.3 
0.5  to  1.8 

04 

0.4 


10.8 


9.3  to  10.9 
8.9 

I  5  to  6.2 
10.8 
12.7 


IX.  Fuel  Value  100-200  Calories  per  Pound 


Beets 

Cabbage 

Carrots 

Green  corn 

Lemons 

Oranges 

Soups  (canned) 

Spinach 

Squash 

Tomatoes  (canned). 


20.0 
15  o 
20.0 
61.0 
30.0 
27.0 


70 

0 

77 

7 

70 

6 

29 

4 

62 

5 

63 

4 

91 

0  to  92.8 

91 

6  to  92.8 

44.2 

92 

5  to 

97-9  1 

13 
14 
0.9 

1.2 

0.7 

0.6 
2.9  to  SO 
1.8  to  2.4 

0.7 
0.3  to  1.7 


0.4 
0.5 

0.1 
0.2  to  0.8 
0.2  to  0.5 

0.2 

O.I  to  0.3 


7.7 
48 

7  4 
7-7 
5  9 
8.5 
0.6  tos  7 
31  t03.4 

4  5 
1.4  to  8.1 


X.   Fuel  Value  io-ioo  Calories  per  Pound 


Asparagus 

Bouillon   (canned) 
Celery 
Cucumbers 
Watermelons 


94.0 
96.5  to  96.7 
75.6 
81. 1 
37.5 


1.8 
.7  to  2.6 
09 
0.7 
0.2 


0.2 

0.0  to  o. 


0.2 
O.I 


3-3 
.  I  to  0.3 
26 
2.6 

3.1 


I20  AIR,   WATER,  AND   FOOD 

complete  nutrition.  The  nutritive  ratio,  or  the  proportion  of 
nitrogenous  to  non-nitrogenous  food,  must  be  maintained  in  the 
proportion  of  i  to  3,  or  at  least  i  to  5. 

The  preceding  table  of  one  hundred  common  food-materials 
is  arranged  in  the  order  of  calorific  or  energy-giving  power,  but 
in  considering  the  food  value  of  any  one  substance  its  nitro- 
gen content  must  also  be  considered,  and  such  combinations 
made  as  will  yield  the  requisite  elements  for  a  well-balanced 
ration. 

From  even  a  cursory  examination  of  the  table  it  will  be  seen 
how  widely  some  of  the  foodstuffs  differ  under  differing  con- 
ditions of  soil  moisture,  fertilization  in  the  case  of  plants,  and 
of  fatness  or  leanness  in  animals,  of  method  of  preparation  or  of 
combination  in  cooked  foods. 

Therefore  examinations  of  materials  are  imperative  if  there  is 
to  be  any  basis  of  calculation.  In  an  institution  where,  for 
instance,  flour  forms  two-thirds  of  the  daily  ration,  if  it  con- 
tains the  lowest  per  cent  of  nitrogen  it  may  not  furnish  sufficient 
proteid  for  a  well-balanced  ration,  or  if  the  meat  used  is  very 
lean  there  may  not  be  fat  enough  for  the  best  nutrition. 

The  great  variation  in  the  proportion  of  water  leads  to  many 
surprises,  and  the  amount  of  unedible  material  is  to  be  con- 
sidered. The  uneducated  provider  buys  oysters  under  the 
impression  that  he  is  furnishing  food  of  high  value,  and  does 
not  distinguish  between  potatoes  and  rice. 

In  the  present  state  of  our  knowledge,  the  best  use  to  which 
we  can  put  such  tables  and  analyses  is  as  a  check  against  gross 
errors  of  diet,  which  are  found  with  alarming  frequency  espe- 
cially among  children  and  students,  those  who  can  least  afford  to 
make  them.  References  will  be  found  in  the  Bibliography  to 
works  for  further  study  along  these  lines. 

Dietaries.  —  A  dietary  is  simply  a  known  amount  of  food  of 
known  composition  per  person  per  day,  week,  or  month. 

What  is  called  a  standard  dietary  is  such  a  combination  of 
food-materials  as  shall  furnish  the  amounts  held  to  be  neces- 
sary.    The  following  are  examples  of  such  standard  dietaries: 


FOOD   IN  RELATION  TO  HUMAN  LIFE 


121 


Approximate  amounts 
required  daily  by 

Nitrogenous, 
grams. 

Fats, 
grams. 

Carbohydrates, 
grams. 

Calories. 

Child  of  6-9 

Child  of  9-14 

Adult  at  rest 

62 

78 

100 

100 

125 

45 
45 
75 
90 
125 

200 
281 
380 

450 
500 

1593 
1890 
2665 

Adult  at  moderate  work.  . 
Adult  at  hard  work 

3092 
3725 

(In  feeding  experiments  from  10  to  20  per  cent  more  must  be  allowed  for  waste 
and  indigestibility.) 

From  the  table  on  page  ii8  may  be  selected  such  food  as  will 
give  the  required  quantities  in  variety  enough  to  suit  any  taste. 
That  which  the  table  cannot  give  is  the  per  cent  of  each  which, 
under  any  given  condition,  will  be  utilized  by  the  person  fed. 
The  strength  of  the  digestive  juices,  exercise,  fresh  air,  the 
cooking,  the  mixing  of  the  foods,  the  habits  of  mind  as  to  food, 
the  customs  of  the  family,  all  influence  this  utilization,  so  that 
other  means  must  be  restored  to  in  order  to  gain  an  idea  of 
what  is  practicable.  This  is  done  by  taking  account  of  the  food 
of  persons  free  to  choose;  of  those  in  different  countries,  in 
different  circumstances,  and  using  a  great  variety  of  materials. 
Since  Voit  made  his  standard  dietary  in  1870,  many  hundreds, 
at  least,  have  been  so  gathered  in  the  United  States  alone  — 
more  than  two  hundred  since  1886.  All  the  information  thus 
gained  goes  to  confirm  the  theoretical  standard,  and  also  to 
show  how  much  depends  upon  suitable  preparation  and  com- 
bination.    These  last  two  things  help  each  other. 

As  food  is  ordinarily  prepared,  about  10  per  cent  must  be 
deducted  for  indigestibiHty  in  a  customary  mixed  diet,  and 
about  10  per  cent  more  for  the  refuse  or  waste  of  food  as  pur- 
chased, so  that  of  the  total  pounds  of  meat,  vegetables,  and 
groceries  some  20  per  cent  is  of  no  final  service  in  the  body.  It 
is  immaterial  whether  this  amount  is  subtracted  from  the  final 
calculation  or  whether  the  higher  figures  be  taken,  that  is, 
whether  125  grams  of  proteid  as  purchased  or  100  grams  final 
utility  is  used.  There  will  be  an  unknown  limit  in  either  case. 
According  to  late  experiments   100  grams  of  proteid  is  high. 


122  AIR,   WATER,   AND   FOOD 

The  waste  of  fats  is  less  in  proportion  as  the  dietary  is  a  restricted 
one. 

Knowledge  of  Food  Values  Necessary.  —  The  most  serious 
aspect  of  the  food  question  is  that  the  taking  of  it  is  voluntary, 
not,  like  air,  a  necessity  beyond  control,  and  that  the  most 
fantastic  ideas  are  allowed  to  rule.  The  day-laborer  is  in  Httle 
danger,  since  his  food  demand  is  made  strong  by  out-of-door 
exercise;  but  the  student  who  shuts  himself  up  in  hot,  close 
rooms,  and  who  does  not  look  upon  food  as  his  capital,  but  only 
as  a  disagreeable  task  or  an  amusement,  is  in  great  danger,  as 
is  he  who,  having  heard  that  one  can  live  on  a  few  cents  a  day, 
proceeds  to  try  it  without  knowledge,  and  suffers  a  loss  of  effi- 
ciency for  years  or  for  all  his  Hfe. 

It  is  not  nearly  so  difficult  to  acquire  a  working  knowledge 
of  food  values  as  of  whist  or  golf,  so  that  on  entering  a  restaurant 
a  suitable  menu  may  be  made  up  within  one's  allowance.  It 
is  only  necessary  to  correct  prevailing  impressions  and  rein- 
force one's  experience. 

Figs,  dates,  raisins  and  prunes  are  apt  to  be  regarded  as 
luxuries  instead  of  as  rich  food-substances  of  a  most  digestible 
kind  when  freed  from  skin  and  seed.  Nuts  are  a  much  neg- 
lected form  of  wholesome  food,  admirably  suited  to  a  winter 
table  from  their  richness  in  fat,  and  also  furnishing  muscular 
energy,  as  is  seen  in  the  agile  squirrel,  and  is  proved  by  many 
human  examples.  With  nuts,  however,  must  be  taken  fruits 
or  other  bulky  foods,  to  balance  the  concentration.  The  some- 
what compact  and  oily  substance  must  be  finely  divided  and 
freed  from  its  astringent  skin. 

In  distinction  from  these  rich  foodstuffs,  we  find  oranges, 
apples,  etc.;  the  usual  garden  vegetables,  asparagus,  lettuce, 
etc.,  which  while  they  fill  an  important  place  in  the  dietary, 
add  little  directly  to  the  energy  of  the  body  and  need  not  be 
considered  except  as,  by  their  flavor  or  aesthetic  stimulus,  they 
add  to  the  efficiency  of  the  rest. 

The  foods  which  furnish  the  greatest  nutrition  for  the  least 
money  are   such  materials  as  corn  meal,   wheat  flour,   milk, 


FOOD   IN  RELATION  TO  HUMAN   LIFE  123 

beans,  cheese  and  sugar.  The  expensive  cuts  of  meat,  high- 
priced  breakfast  cereals  and  the  Uke,  add  but  Httle  to  the  nu- 
tritive value  but  greatly  increase  the  cost  of  living.  A  meal  of 
lettuce  dressed  with  oil,  eaten  with  bread  and  cheese,  fulfils  all  the 
requirements  of  nutrition,  and  may  cost  five  cents.  The  same 
food  value  from  sweet  breads,  grape-fruit,  etc.,  might  cost  a 
dollar.  Incorrect  ideas  in  regard  to  food  values,  and  prejudice 
inherited  or  acquired  against  certain  foods,  have  too  often 
resulted  in  excluding  wholesome  and  nutritious  articles  from 
the  dietary  and  decreasing  thereby  the  efficiency  of  the  human 
machine. 


CHAPTER  VIII 

THE   PROBLEM   OF   SAFE   FOOD.      ADULTERATION  AND 
SOPHISTICATION 

Adulteration  grows  largely,  if  not  almost  entirely,  from  ex- 
cessive competition.  Nearly  every  article  of  common  food  has 
been  found  at  one  time  or  another  to  be  adulterated,  yet  manu- 
facturers testify  that  they  wihingly  would  stop  this  addition  of 
foreign  material  if  they  could  be  sure  that  their  competitors 
would  stop  also.  Other  causes  there  are  also:  demands  for 
goods  out  of  season;  for  perishable  products  which  must  come 
many  miles;  the  failure  of  the  supply  of  a  given  substance  to 
meet  a  continuing  demand;  all  of  these  lead  to  adulteration, 
imitation  and  substitution. 

To  many  people  otherwise  intelligent,  the  term  adulterated  food 
is  synonymous  with  poisoned  food.  With  others,  thanks  to 
alarming  newspaper  articles,  not  wholly  disinterested,  the  general 
impression  is  far  beyond  the  reality.  It  is  not  necessary  to 
use  poisonous  or  even  deleterious  material;  it  needs  only  to  mix 
with  the  food  material  some  substance  cheaper  but  harmless, 
to  make  some  change  in  the  outward  appearance  of  the  article 
so  that  people  shall  not  recognize  the  familiar  substance,  and 
then  to  herald  far  and  wide  the  discovery  of  a  new  process  by 
which  the  food  value  is  greatly  enhanced.  "Things  are  not 
what  they  seem"  is  nowhere  more  true  than  in  the  case  of 
foods. 

Definition  of  Adulteration.  —  To  adulterate  is  "to  debase,^''  "to 
make  impure  by  an  admixture  of  baser  materials."  The  word 
"adulterated  "  refers  to  any  food  to  which  any  foreign  substance, 
not  a  proper  portion  of  the  food,  has  been  added.  It  does  not 
matter  whether  the  added  material  is  of  greater  value  than  the 
food  itself.     The  addition  of  coffee  to  cereal  or  substitute  coffees, 

124 


ADULTERATION   AND   SOPHISTICATION  125 

is  properly  held  to  be  an  adulteration.  Deterioration  should  not 
be  mistaken  for  adulteration.  People  who  are  not  wholly  familiar 
with  the  appearance  of  a  food  or  the  chemical  and  physical 
changes  which  it  may  undergo,  think  that  if  it  does  not  taste  just 
right  or  look  just  right  that  it  must  be  adulterated.  Appearance 
has  slight  relation  to  the  purity  of  the  article  in  these  days  of 
paint,  polish  and  powder. 

Some  forms  of  adulteration  are  more  properly  described  under 
the  head  of  misbranding,  that  is,  referring  to  foods  incorrectly  de- 
scribed by  the  label.  WTiilc  the  significance  is  not  exactly  the 
same  as  that  of  the  word  adulterated,  yet  the  two  may  sometimes 
be  applied  to  the  same  product.  For  instance,  the  addition  of 
starch  to  sausage  to  conceal  the  use  of  excessive  amounts  of  water 
and  of  fat  constitutes  an  adulteration,  which  would  not  be  the  case 
if  the  article  were  properly  branded  to  show  the  presence  of  the 
added ''filler." 

To  adulterate  the  coin  of  the  realm  or  the  liquor  of  the  bar  with 
a  baser  metal  or  an  imitation  whisky  is  a  heinous  offence.  So  is 
the  mixture  of  milk  with  the  baser  article,  water,  which  thereby 
lowers  its  food  value.  But  the  "wretched  sophistry"  which  ob- 
scures the  nature  of  things  on  a  package  of  prepared  food  mis- 
leads more  persons  and  inflicts  more  injury  upon  the  community 
than  the  other,  yet  goes  unrebuked.  The  most  barefaced  asser- 
tions are  printed  in  magazines,  and  "pure-food  shows"  only  whet 
the  appetite  for  something  new. 

Legal  Definition  of  Adulteration  and  Misbranding.  —  In  the 
Federal  Pure  Food  Law,  commonly  known  as  the  Food  and  Drugs 
Act  of  June  30,  1906,  adulteration  and  misbranding  are  thus 
defined : 

Sec.  7.  That  for  the  purposes  of  this  Act  an  article  shall  be 
deemed  to  be  adulterated: 

In  the  case  of  food : 

First.  If  any  substance  has  been  mixed  and  packed  with  it  so 
as  to  reduce  or  lower  or  injuriously  affect  its  quality  or  strength. 

Second.  If  any  substance  has  been  substituted  wholh-  or 
in  part  for  the  article. 


126  AIR,  WATER,  AND   FOOD 

Third.  If  any  valuable  constituent  of  the  article  has  been 
wholly  or  in  part  abstracted. 

Fourth.  If  it  be  mixed,  colored,  powdered,  coated,  or  stained 
in  a  manner  whereby  damage  or  inferiority  is  concealed. 

Fifth.  If  it  contains  any  added  poisonous  or  other  added  dele- 
terious ingredient  which  may  render  such  articles  injurious  to 
health :  Provided,  That  when  in  the  preparation  of  food  products 
for  shipment  they  are  preserved  by  any  external  application  ap- 
plied in  such  manner  that  the  preservative  is  necessarily  removed 
mechanically,  or  by  maceration  in  water,  or  otherwise,  and  direc- 
tions for  the  removal  of  said  preservative  shall  be  printed  on  the 
covering  or  the  package,  the  provisions  of  this  Act  shall  be  con- 
strued as  applying  only  when  said  products  are  ready  for  con- 
sumption. 

Sixth.  If  it  consists  in  whole  or  in  part  of  a  filthy,  decomposed, 
or  putrid  animal  or  vegetable  substance,  or  any  portion  of  an 
animal  unfit  for  food,  whether  manufactured  or  not,  or  if  it  is  the 
product  of  a  diseased  animal,  or  one  that  has  died  otherwise  than 
by  slaughter. 

Sec.  8.  That  the  term  "misbranded,"  as  used  herein,  shall 
apply  to  all  drugs,  or  articles  of  food,  or  articles  which  enter  into 
the  composition  of  food,  the  package  or  label  of  which  shall  bear 
any  statement,  design,  or  device  regarding  such  article,  or  the 
ingredients  or  substances  contained  therein  which  shall  be  false  or 
misleading  in  any  particular,  and  to  any  food  or  drug  product 
which  is  falsely  branded  as  to  the  State,  Territory,  or  country  in 
which  it  is  manufactured  or  produced. 

That  for  the  purposes  of  this  Act  an  article  shall  also  be  deemed 
to  be  misbranded: 

In  the  case  of  food : 

First.  If  it  be  an  imitation  of  or  offered  for  sale  under  the  dis- 
tinctive name  of  another  article. 

Second.  If  it  be  labeled  or  branded  so  as  to  deceive  or  mislead 
the  purchaser,  or  purport  to  be  a  foreign  product  when  not  so, 
or  if  the  contents  of  the  package  as  originally  put  up  shall  have 
been  removed,  in  whole  or  in  part,  and  other  contents  shall  have 


ADULTERATION   AND   SOPHISTICATION  127 

been  placed  in  such  package,  or  if  it  fail  to  bear  a  statement  on 
the  label  of  the  c|uantity  or  proportion  of  any  morphine,  opium, 
cocaine,  heroin,  alpha  or  beta  eucaine,  chloroform,  cannabis 
indica,  chloral  hydrate,  or  acetanilide,  or  any  derivative  or  prep- 
aration of  any  such  substances  contained  therein. 

Third.  If  in  package  form,  and  the  contents  are  stated  in  terms 
of  weight  or  measure,  they  are  not  plainly  and  correctly  stated  on 
the  outside  of  the  package. 

Fourth.  If  the  package  containing  it  or  its  label  shall  bear  any 
statement,  design,  or  device  regarding  the  ingredients  or  the  sub- 
stances contained  therein,  which  statement,  design,  or  device  shall 
be  false  or  misleading  in  any  particular :  Provided,  That  an  article 
of  food  which  does  not  contain  any  added  poisonous  or  deleterious 
ingredients  shall  not  be  deemed  to  be  adulterated  or  misbranded 
in  the  following  cases : 

First.  In  the  case  of  mixtures  or  compounds  which  may  be 
now  or  from  time  to  time  hereafter  knowTi  as  articles  of  food, 
under  their  own  distinctive  names,  and  not  an  imitation  of  or 
offered  for  sale  under  the  distinctive  name  of  another  article,  if 
the  name  be  accompanied  on  the  same  label  or  brand  with  a  state- 
ment of  the  place  where  said  article  has  been  manufactured  or 
produced. 

Second.  In  the  case  of  articles  labeled,  branded,  or  tagged 
so  as  to  plainly  indicate  that  they  are  compounds,  imitations, 
or  blends,  and  the  word  "compound,"  "imitation,"  or  "blend," 
as  the  case  may  be,  is  plainly  stated  on  the  package  in  which 
it  is  offered  for  sale:  Provided,  That  the  term  blend  as  used 
herein  shall  be  construed  to  mean  a  mkture  of  like  substances, 
not  excluding  harmless  coloring  or  flavoring  ingredients  used 
for  the  purpose  of  coloring  and  flavoring  only:  And  provided 
Jtiriher,  That  nothing  in  this  act  shall  be  construed  as  requir- 
ing or  compelling  proprietors  or  manufacturers  of  proprietary 
foods  which  contain  no  unwholesome  added  mgredient  to  dis- 
close their  trade  formulas,  except  in  so  far  as  the  provisions  of 
this  act  may  require  to  secure  freedom  from  adulteration  or 
misbranding. 


128  AIR,   WATER,   AND   FOOD 

Extent  of  Adulteration.  —  In  any  discussion  of  the  extent  to 
which  adulterated  foods  are  sold  it  must  be  borne  in  mind  that 
the  adulterated  articles  make  up  only  a  relatively  small  propor- 
tion of  the  food  that  actually  passes  over  the  counter.  Flour,  for 
example,  is  seldom  adulterated;  pepper,  mustard  and  vanilla  ex- 
tract often  are.  For  one  pound  of  these  substances  sold,  looo 
pounds  or  more  of  flour  go  out  from  the  store.  Figures  given  in 
official  reports  of  food  inspection  do  not  represent  the  case  exactly, 
because  the  inspectors  are  trained  men,  and  purchase  samples  of 
those  lines  of  goods  which  experience  has  shown  them  to  be  most 
likely  to  be  adulterated.  Brands  of  foods  which  they  have  reason 
to  believe  are  pure  they  do  not  sample.  Estimated  on  the  total 
quantity  sold,  it  is  doubtful  if  more  than  5  to  10  per  cent  of  the 
food  sold  is  adulterated  in  any  way,  and  these  figures  would  un- 
doubtedly be  much  too  high  for  those  states  in  which  there  is  a 
well-enforced  system  of  food  inspection. 

Character  of  Adulteration.  —  Much  of  the  present  propaganda 
in  the  interests  of  pure  food  and  the  movement  for  the  protection 
of  the  consumer  can  be  summed  up  in  three  words:  "An  Honest 
Label."  In  many  cases  an  accurate  and  true  statement  of  the 
contents  of  the  can  or  package  is  the  only  protection  needed  by 
the  consumer,  and  is  fully  as  efhcient  as  well  as  much  cheaper 
than  prosecutions  or  restrictive  measures.  Many  of  the  terms 
used  on  food  packages  deceive  only  the  ignorant  purchaser. 
"Strictly  pure"  is  a  well-understood  trade  term,  with  a  meaning 
known  to  the  initiated;  the  words  "Home-Made"  may  cover 
some  of  the  most  highly  developed  products  of  synthetic  organic 
chemistry. 

The  cases  in  which  the  adulteration  is  of  a  character  dele- 
terious to  health  are  fortunately  few.  The  use  of  canned  goods 
brings  certain  dangers  in  the  dissolved  metals  from  the  cans  or 
from  the  solder,  also  from  a  careless  habit  of  allowing  foods 
to  stand  in  the  opened  tins.  The  liking  for  bright  green  pickles 
and  peas  leads  to  coloration  by  copper  salts. 

So  rapidly  do  new  substances  come  upon  the  market  that  it  is 
of  little  use  to  put  into  a  general  text-book  definite  statements  of 


ADULTERATION  AND   SOPHISTICATION  1 29 

the  quality  of  many  foods.  A  baking-powder  or  a  spice  which  is 
honestly  made  to-day  may  next  week  pass  into  the  hands  of  un- 
scrupulous dealers  who  please  the  public  and  thereby  salve  their 
consciences. 

To  furnish  what  the  people  think  they  want  has  been  the  rule 
from  the  days  of  an  earlier  generation  of  grocers,  who  divided  a 
barrel  of  cooking-soda  in  halves  and  set  one-half  on  one  side  of 
the  store  for  "saleratus"  and  the  other  on  the  opposite  side  for 
soda,  so  that  there  should  be  no  suspicion  in  the  mind  of  the  cus- 
tomer that  the  packages  came  from  the  same  barrel,  and  yet  each 
might  satisfy  his  individual  preference. 

Names  that  have  passed  down  from  a  former  generation  as 
being  above  reproach  are  now  found  to  cover  adulterated  goods. 
The  trademark  has  passed  into  other  and  less  scrupulous  hands, 
and  the  new  owners  do  not  hesitate  to  trade  upon  the  reputation 
earned  by  their  predecessors.  There  are,  however,  several  phases 
of  the  subject  that  should  be  briefly  mentioned. 

Breakfast  Foods.  —  The  craving  for  something  new  to  stimulate 
a  jaded  appetite  already  spoiled  by  endless  variety  and  bad  com- 
binations has  led  to  the  manufacture  of  a  cereal  preparation  for 
nearly  every  day  in  the  year,  regarding  some  of  which  the  state- 
ment is  made  that  they  are  ''predigested."  No  better  commen- 
tary on  the  laziness  or  wilful  ignorance  of  American  providers 
could  be  made  than  this.  Little  do  the  people  know  about  wheat 
or  cooking  if  they  suppose  that  grain  can  be  changed  by  manipu- 
lation in  any  kind  of  machine  so  as  to  give  greater  food  value  than 
was  contained  in  the  grain.  WTiile  it  is  true  that  some  of  these 
preparations  are  far  better  than  the  half-cooked  grains  found  on 
so  many  tables,  the  fact  remains  that  it  is  the  cook  and  not  the 
substance  which  is  poor.  The  false  statements  on  food  packages 
of  all  kinds  are  so  absurd  that  they  would  defeat  their  own  pur- 
pose were  they  viewed  in  the  light  of  common  sense.  It  is  not 
always  best  to  have  food  which  is  too  easily  digested. 

A  predigested  food  is  quickly  absorbed  into  the  circulation, 
and  hence  a  small  quantity  causes  a  sensation  of  fulness  and  satis- 
faction, which,  however,  soon  passes  away  and  a  faintness  results. 


130  AIR,  WATER,  AND   FOOD 

This  is  especially  true  of  the  sugars  and  dextrins.  Frequent 
meals  should  go  with  easily  absorbed  foods.  The  rapid  digestion 
is  the  cause  of  much  pernicious  eating  of  sweets  between  meals, 
which  satisfies  the  appetite  for  the  time  being  and  prevents  sub- 
stantial quantities  of  other  foods  being  taken  at  the  time  they 
are  offered. 

From  a  study  of  analyses  of  a  large  number  of  foods  the  fol- 
lowing conclusions  are  drawn  by  F.  W.  Robison:  * 

1.  The  breakfast  foods  are  legitimate  and  valuable  foods. 

2.  Predigestion  has  been  carried  on  in  the  majority  of  them 
to  a  limited  degree  only. 

3.  The  price  for  which  they  are  sold  is  as  a  rule  excessive  and 
not  in  keeping  with  their  nutritive  values. 

4.  They  contain,  as  a  rule,  considerable  fibre  which,  while 
probably  rendering  them  less  digestible,  at  the  same  time,  may 
render  them  more  wholesome  to  the  average  person. 

5.  The  claims  made  for  many  of  them  are  not  warranted  by 
the  facts. 

6.  The  claim  that  they  are  far  more  nutritious  than  the  wheat 
and  grains  from  which  they  are  made  is  not  substantiated. 

7.  They  are  palatable  as  a  rule  and  pleasing  to  the  eye. 

8.  The  digestibility  of  these  products  as  compared  with  highly 
milled  goods,  while  probably  favorable  to  the  latter,  does  not  give 
due  credit  to  the  former,  because  of  the  healthful  influence  of  the 
fibre  and  mineral  matter  in  the  breakfast  foods. 

9.  Rolled  oats  or  oatmeal  as  a  source  of  protein  and  of  fuel  is 
ahead  of  the  wheat  preparations,  excepting  of  course  the  special 
gluten  foods,  which  are  manifestly  in  a  different  class. 

In  general,  the  cost  of  these  foods  is  low  if  they  are  considered 
merely  as  confections  to  please  the  taste,  but  they  are  expensive 
foods  regarded  as  substitutes  for  the  ordinary  cereal  products. 

This  is  well  shown  in  the  following  table  in  which  the  fuel 
value  of  breakfast  foods  and  other  common  food  products  ob- 
tained for  a  given  sum  is  graphically  compared. 

*  Mich.  Agr.  Expt.  Sta.,  Bull.,  211  (1904). 


ADULTERATION  AND    SOPHISTICATION 


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132  AIR,   WATER,   AND   FOOD 

Colors  and  Preservatives  in  Food.  —  For  many  years  such  sub- 
stances as  alcohol,  vinegar,  sugar,  salt,  and  the  like,  have  been 
used  to  preserve  food.  Such  materials  are  commonly  held  to  be 
harmless  to  persons  of  sound  digestion  if  used  in  moderate 
amounts.  Within  recent  years,  however,  there  has  been  a  con- 
stantly increasing  tendency  toward  the  use  in  food  products  of 
such  powerful  antiseptics  as  formaldehyde,  salicylic  and  benzoic 
acids  and  their  salts,  and  boric  acid.  An  important  distinction 
to  be  borne  in  mind  between  this  class  of  preservatives  and  those 
first  named  is  that  the  former  when  used  in  food  in  quantity  suffi- 
cient to  preserve  it  make  their  presence  known  to  the  consumer 
by  either  their  taste  or  odor.  With  the  chemical  preservatives, 
however,  an  intimation  of  their  presence  is  conveyed  to  the  con- 
sumer only  by  a  statement  on  the  label.  It  is  the  general  feeling 
among  those  engaged  in  the  enforcement  of  the  food  laws  that 
the  common  use  of  these  preservatives  should  be  forbidden,  or 
that  they  should  be  allowed  only  under  certain  definite  restric- 
tions. The  question  is  not  one  of  their  possible  harmful  effect 
only,  although  it  cannot  be  successfully  denied  that  their  unre- 
stricted use  would  lead  to  grave  danger  to  health,  especially  in  the 
case  of  invalids  and  children,  or  those  with  various  degrees  of 
digestive  efficiency.  It  seems  reasonable  to  infer  that  the  proc- 
esses of  digestion,  being  largely  the  result  of  bacterial  and 
enzymic  action,  will  be  retarded  or  interfered  with  to  a  greater 
or  less  extent  by  substances  which  inhibit  bacterial  action  in 
food. 

There  is,  however,  another  reason  for  objecting  to  the  use  of 
chemical  preservatives.  By  their  use  much  food  that  is  unwhole- 
some and  unfit  for  consumption  can  be,  and  is,  placed  upon  the 
market  with  no  warning  to  the  consumer.  ''The  man  who  adds 
formaldehyde  to  his  milk  takes  down  the  danger  signal,  but  does 
not  remove  the  danger." 

Similarly,  objections  can  be  made  to  the  use  of  coal-tar  colors 
in  foods.  There  are  hundreds  of  food  packages  which  would 
never  leave  the  grocers'  shelves  were  it  not  for  the  fact  that  by 
the  use  of  artificial  color  their  true  composition  and  the  actual 


ADULTERATION   AND    SOPHISTICATION  133 

nature  of  the  materials  from  which  they  are  made  is  hidden. 
Apart  from  any  question  as  to  the  harmfulness  of  these  dyes 
there  is  ample  reason  for  their  use  being  strictly  regulated  by 
official  action,  in  that  their  use  except  under  such  supervision 
allows  the  manufacturer  to  sell  inferior  articles  under  the  appear- 
ance of  standard  foods;  it  permits  the  customer  to  be  misled  as 
to  the  strength  and  purity  of  the  product  that  he  buys;  the  age 
and  past  history  of  the  product  may  be  made  a  sealed  book; 
finally,  by  the  use  of  coloring,  an  unwholesome  and  improper 
food  may  be  put  upon  the  market. 

Summary.  —  The  chief  dangers  in  food  are  from  wrong  pro- 
portions of  proteid,  fat,  and  carbohydrates,  from  fermentable  and 
irritating  decompositions,  from  bad  methods  of  cooking  and 
unsuitable  combinations,  from  transmission  of  micro-organisms 
either  by  exposure  to  dust  or  by  contact  with  filthy  hands  or  ves- 
sels, to  a  favorable  medium  for  the  growth  of  pathogenic  germs, 
from  unsuitable  food  scientifically  disguised. 

From  this  hasty  survey  it  will  be  seen  how  little  danger  to 
health  is  incurred  if  only  reasonable  care  is  taken  and  if  the  always 
doubtful  articles  are  avoided. 

Take,  for  instance,  that  most  commonly  adulterated  class, 
spices.  Who  will  say  that  it  may  not  be  better  to  eat  corn  and 
buckwheat  and  ground  peas  than  pure  pepper?  Rice  is  certainly 
a  more  wholesome  food  than  ginger,  and  starch  than  soda.  Glu- 
cose is  even  more  easily  absorbed  than  cane-sugar.  These  are 
cases  of  frauds  on  the  pockets,  but  possibly  blessings  in  disguise 
for  the  stomachs.  When  any  community  is  so  ignorant  as  to  per- 
mit of  such  glaring  cases  of  adulteration  as  coal-tar  dyes  in  food, 
and  gypsum  in  cream  of  tartar,  they  deserve  to  suffer.  It  is 
knowledge  on  the  part  of  each  intelligent  citizen  which  will  mend 
matters,  even  if  it  is  only  that  kind  of  empirical  knowledge  that 
one  is  forced  to  learn  in  relation  to  electricity  and  steam  in  order 
to  live  in  a  modern  house. 

This  knowledge  is  now  easily  obtained  through  the  city,  state 
and  governmental  laboratories,  and  their  publications  are  acces- 
sible to  all  who  can  read  and  write.     There  is  therefore  no  excuse 


134  AIR,  WATER,  AND   FOOD 

for  general  ignorance  and  credulity  as  to  trade  preparations  of 
foods,  any  more  than  for  the  degrading  habit  of  purchasing  patent 
medicines  to  remedy  the  ills  caused  by  the  misuse  of  food.  Both 
together  form  the  saddest  commentary  on  human  weakness  and 
lack  of  rational  thought. 


CHAPTER  IX 

ANALYTICAL   METHODS 

In  the  discussion  of  the  methods  employed  for  the  examination 
of  food-materials,  only  a  few  typical  substances  have  been  con- 
sidered, and  the  processes  given  are  such  as  to  bring  into  promi- 
nence the  scientific  aspect  rather  than  the  technical  detail  of  the 
subject;  at  the  same  time  it  is  hoped  that  a  sufficient  variety  of 
methods  is  given  to  enable  the  student  to  gain  considerable  expe- 
rience in  the  necessarily  short  time  which  can  be  alloted  to  the 
subject. 

Both  on  account  of  its  importance  as  a  food-material  and 
on  account  of  its  availability  for  the  various  tests,  milk  has  been 
chosen  as  a  type  of  animal  food;  moreover,  it  may  be  made  to 
serve  as  an  excellent  example  of  the  changes  to  which  food-ma- 
terials are  liable  through  the  growth  of  the  micro-organisms. 
The  analysis  of  milk  includes  determinations  of  specific  gravity, 
water,  or  total  solids,  ash,  fat,  proteids  and  sugar,  the  separation 
of  casein  and  albumin,  and  the  detection  of  preservatives,  color- 
ing matters,  and  added  water. 

The  breakfast  cereals  are  taken  as  typical  of  vegetable  foods. 
The  examination  which  may  be  made  of  this  class  includes  the 
determination  of  moisture,  ash,  fat,  nitrogen  and  proteids, 
starch,  cellulose,  and  the  products  of  peptonization  and  sacchari- 
fication. 

The  nature  and  composition  of  the  various  fats  and  oils  is 
briefly  illustrated  by  the  examination  of  butter  and  the  deter- 
mination of  the  principal  "  constants  "  of  the  butter-fat. 

The  results  of  fermentation  are  illustrated  by  the  deter- 
mination of  alcohol  in  beer,  wine,  meat  extracts,  patent  medi- 
cines and  "temperance  drinks,"  flavoring  essences  and  the  like. 
The  determination  of  the  relative  proportion  of  volatile  and 

135 


136 


AIR,  WATER,  AND  FOOD 


fixed  acids,  of  the  saccharine  products  of  malting,  and  of  volatile 
oils  or  flavoring  principles,  is  also  instructive. 

A  more  elaborate  discussion  of  the  methods  used  in  food 
analysis  and  of  the  interpretation  of  results  will  be  found  in 
the  larger  works  upon  the  subject.  As  reference  books  for  the 
use  of  the  student  in  the  laboratory,  the  following,  in  the  author's 
experience,  have  been  found  especially  helpful:  Leach:  Food 
Inspection  and  Analysis;  Sherman:  Organic  Analysis;  Rolfe: 
The  Polariscope  in  the  Laboratory;  Bulletin  107,  Bureau  of 
Chemistry. 

MILK 

Milk  is  a  food  material  of  somewhat  complex  and  variable 
composition  but  can  be  described  as  essentially  an  aqueous 
solution  of  milk  sugar,  mineral  salts  and  soluble  albumin  con- 
taining suspended  globules  of  fat  and  partially  dissolved  casein. 

General  Composition.  —  In  approximate  figures  the  average 
percentage  composition  of  milk  may  be  stated : 

Per  cent 

Total  solids 12.8 

Fat 3-8 

Protein 3.6 

Ash 0.7 

Milk  sugar 4.7 

Solids  not  fat 9.0 

From  these  figures  there  may  be  in  normal  milk  quite  decided 
variations  and  figures  have  been  reported  which  differ  widely 
from  them,  some  of  the  discrepancies  of  the  older  analyses  being 
undoubtedly  due  to  the  imperfect  methods  of  analysis  employed. 

Lythgoe  *  states  that  all  milk  completely  drawn  from  healthy 
cows  will  fall  between  the  following  limits : 


Extreme  limits, 
per  cent. 


Usual  limits, 
per  cent. 


Herd  milk, 
per  cent. 


Total  solids.  . 

Fat 

Protein 

Ash 

Milk  sugar.  .  . 
Solids  not  fat. 


10. 0-17.0 
2.2-  9.0 
2.1-  8.5 
0.6-  0.9 
4.0-  6.0 
7.5-11.0 


5-16.0 
8-  7.0 

5-  4-5 
7-  0.8 

2-5-5 
7-10.0 


I I. 8-15.0 
3.2-  6.0 
2.5-  4.0 
0.7-  0.8 

4-3-  5-3 
8.0-  9.5 


*  Bull.  Mass.  Slate  Bd.  Health,  1910,  p.  419. 


ANALYTICAL  METHODS 


137 


Variations  in  Composition.  —  Besides  variations  in  compo- 
sition which  may  be  due  to  individual  cows  there  are  also  certain 
well-established  differences  due  to  environment  or  to  racial  influ- 
ences.    Among  the  more  important  of  these  are: 

(i)  The  Breed  of  the  Cow.  —  Some  breeds  yield  quantity, 
others  quality.  The  Jersey  and  Guernsey  cattle,  for  instance, 
give  comparatively  small  quantities  of  milk  rich  in  fat;  the 
Holstein  cows,  on  the  other  hand,  yield  much  larger  amounts  of 
milk  of  decidedly  lower  solids  and  fat  content.  These  differ- 
ences are  well  simimarized  in  the  following  table  based  on  data 
collected  by  the  Massachusetts  Board  of  Health.* 


Breed. 


Jersey 

Guernsey. . 
Ayrshire. . . 
Dutch  Belt 
Holstein. . . 


Specific 
gravity. 

Total 

Fat, 

Protein, 

Ash, 

Solids 

solids, 

per 

per 

per 

not  fat, 

per  cent. 

cent. 

cent. 

cent. 

per  cent. 

I   034 

14-57 

5-40 

3-54 

0.78 

9.17 

I    034 

14.40 

5.00 

3-77 

0.77 

9.40 

1.032 

12.57 

4.00 

2.90 

0.77 

8.57 

1.032 

12.03 

3.60 

2.62 

0.68 

8.43 

1.032 

II  .96 

3-35 

2.99 

0.69 

8.61 

Milk 

sugar, 

per  cent. 


If  individual  differences  are  eliminated  and  only  fully  drawn 
mixed  milk  from  herds  is  considered,  the  variation  due  to  breed 
is  the  factor  of  the  greatest  influence  in  permanently  affecting 
the  composition  of  milk. 

(2)  The  Time  of  Year.  —  The  poorest  milk  is  produced  during 
the  spring  and  early  summer  months,  the  richest  during  the 
seasons  of  autumn  and  early  winter,  when  the  cattle  are  getting 
a  smaller  proportion  of  green  feed.  This  difference  is  clearly 
shown  in  the  following  table  f  which  gives  the  seasonal  average 
for  16  years: 


Total  solids, 
per  cent. 

Fat. 
per  cent. 

Solids  not  fat, 
per  cent. 

Nov  .—Jan 

13   04 
12.72 
12.66 
13  03 

4. II 
3-88 
389 
4-25 

8.93 
8.84 
8.77 
8.78 

Feb.  -Apr 

May  —  Aug 

Oct.  -Nov 

*  Bur.  of  Chan.,  Bull.  132,  p.  129. 

t  Richmond:  Dairy  Chemistry,  p.  126. 


138 


AIR,   WATER,   AND    FOOD 


This  variation  in  composition  of  milk  between  the  pasture-fed 
and  the  stall-fed  season  has  in  the  past  received  legal  recognition 
in  the  fixing  of  milk  standards.  In  Massachusetts  for  many 
years  the  legal  standard  for  total  solids  was  set  at  13  per  cent 
in  the  winter  months  and  at  12  per  cent  in  the  summer  season. 

(3)  Time  of  Day.  —  Milk  which  has  been  drawn  in  the  even- 
ing is  nearly  always  richer  in  fat  than  the  morning  milk  as  shown 
in  the  following  averages: 


Morning  milk. 
Evening  milk. 


Specific 
gravity. 


.0322 
.0318 


Total  solids. 


12.53 
12.94 


Fat. 


4.04 


(4)  "Fore"  milk  vs.  "strip pings. '^  —  If  different  portions  of 
the  whole  quantity  of  milk  obtained  at  a  single  milking  are  ex- 
amined separately  they  will  be  found  to  show  marked  differences 
in  fat  content,  especially  as  between  the  first  and  last  portions. 
The  other  constituents  of  the  milk  do  not  vary  so  greatly  as 
the  fat.  The  first  portions  of  milk,  the  "fore"  milk,  contain 
much  less  fat  than  do  the  last  portions  or  "strippings."  The 
following  figures,  due  to  Van  Slyke,  illustrate  this  point: 


Per  cent  of  fat  in  milk. 

Cow  I. 

Cow  2. 

Cow  3. 

First  portion  drawn 

Second  portion  drawn 

Third  portion  drawn 

Fourth  portion  drawn  (strippings) . 

0.90 
2.60 

5-35 
9.80 

1.60 
3.20 
4.  10 
8.10 

1.60 

3-25 
5.00 
8.30 

This  difference  in  composition  is  explained  by  the  separation 
of  the  milk  while  in  the  udder  of  the  cow,  cream  rising  to  the 
top  just  as  would  happen  if  the  milk  stood  in  a  vessel,  hence 
being  drawn  last.  Dishonest  dairymen  have  in  the  past  taken 
advantage  of  this  fact  in  adulteration  cases,  by  having  the  cows 
partially  milked  in  the  presence  of  unsuspecting  witnesses,  the 
resulting  "known  purity"  milk  being  thus  largely  "fore"  milk. 


ANALYTICAL  METHODS  139 

In  general  it  will  be  found  that  to  whatever  causes  the  varia- 
tions noted  in  the  composition  of  milk  are  due,  the  differences 
are  shown  much  more  in  the  fat  than  in  any  other  constituent. 
The  protein  is  also  variable,  although  to  a  somewhat  less  extent, 
and  the  milk  sugar  and  ash  are  much  more  nearly  constant. 

METHODS    OF   ANALYSIS 

Preparation  of  the  Sample.  — •  Since  the  cream  will  rise  on  a 
sample  of  milk  sufficiently  in  five  minutes  to  destroy  the  uni- 
formity of  the  sample,  great  care  must  be  used  in  taking  a  portion 
for  analysis  to  ensure  that  it  represents  a  fair  average  of  the 
milk.  The  best  way  is  to  pour  the  milk  from  the  containing 
vessel  into  another  and  back  again  several  times,  or  if  this  is 
impracticable  it  should  be  thoroughly  stirred  before  being  sam- 
pled. If  the  analytical  sample  has  stood  for  any  appreciable 
time  it  should  be  mixed  by  pouring  back  and  forth  before  a 
portion  is  removed  to  test,  otherwise  concordant  results  cannot 
be  obtained.  Do  not  shake  the  sample  since  this  tends  toward 
a  separation  of  the  fat. 

Specific  Gravity.  —  This  is  usually  taken  with  a  special  form 
of  hydrometer,  known  as  a  lactometer.  The  Quevenne  lactom- 
eter has  a  scale  graduated  into  25  equal  parts,  extending  from 
15  to  40,  corresponding  to  specific  gravities  from  1.015  to  1.040. 
The  best  form  of  instrument  is  that  provided  with  a  thermometer. 

The  lactometer  is  graduated  to  give  correct  results  at  60°  F. 
(15.6°  C.)  and  the  reading  should  be  made  at  approximately 
that  temperature,  between  55  and  65  degrees,  and  then  corrected 
to  standard  temperature.  This  may  be  done  by  adding  o.i 
to  the  reading  for  each  degree  F.  above  60°  F.,  or  subtracting 
0.1  for  each  degree  F.  below  60°  F.  If  the  temperature  is 
read  in  Centigrade  degrees  the  correction  may  be  made  by  the 
table  on  page  216. 

The  New  York  Board  of  Health  lactometer  has  a  scale  reading 
o  in  water,  and  100  in  milk  with  a  specific  gravity  of  1.029,  which 
is  taken  as  the  lowest  limit  for  pure  milk.  The  instrument  is 
used  in  the  same  manner  as  the  Quevenne  lactometer  and  the 


I40  AIR,   WATER,  AND   FOOD 

readings  can  readily  be  converted  into  degrees  of  the  latter 
instrument. 

Notes.  —  The  specific  gravity  of  milk  fat  is  about  0.93 ;  of  tjie 
soHds  not  fat  approximately  1.5.  The  specific  gravity  of  the 
milk  itself  is  thus  a  function  of  the  two;  the  former  lowers  it, 
the  latter  increases  it.  As  would  be  expected  from  the  variable 
composition  of  milk,  the  specific  gravity  is  also  a  variable.  The 
values  for  normal  milk  from  a  herd,  however,  will  usually  fall 
between  1.030  and  1.034. 

Taken  by  itself  the  specific  gravity  is  of  Uttle  value  in  showing 
adulteration.  The  addition  of  water  lowers  the  specific  gravity 
of  milk;  the  removal  of  cream  raises  it,  this  being  the  lighter 
portion  of  the  milk.  It  is  therefore  theoretically  possible  by 
skilful  manipulation  to  both  skim  and  water  a  sample  and  still 
have  its  specific  gravity  correspond  to  that  of  normal  milk. 
Such  a  sample  would,  however,  be  readily  recognized  by  one 
familiar  with  the  appearance  of  the  genuine  product. 

The  lactometer  reading  is  of  value  in  rapid  analysis  of  milk 
for  calculating  the  soHds  in  connection  with  the  Babcock  method 
of  fat  determination  (see  page  148). 

Total  Solids.  —  Use  a  platinum  dish  having  a  flat  bottom 
about  2I  inches  in  diameter.  Ignite  and  weigh  the  dish  accu- 
rately, then  add  about  5.1  grams  to  the  weights  on  the  balance- 
pan.  With  a  pipette  dehver  5  c.c.  of  the  well-mixed  milk  into 
the  dish  and  weigh  the  whole  as  rapidly  as  possible  to  the  nearest 
milHgram.  Evaporate  the  milk  to  dryness  on  the  water-bath 
and  then  dry  it  in  the  oven  at  100°  C.  to  constant  weight.  Three 
hours  drying  is  usually  sufficient. 

Notes.  —  It  is  important  that  the  milk  should  be  dried  in  a 
thin  layer,  so  that  the  removal  of  the  water  shall  take  place  as 
quickly  as  possible.  Under  these  conditions  the  residue  ob- 
tained is  nearly  white,  but  if  the  process  be  prolonged,  it  may 
have  a  brownish  color  from  the  caramelization  of  the  sugar. 

If  it  is  not  desired  to  determine  ash  on  the  same  weighed 
portion  as  used  for  the  solids,  lead  foil  dishes  or  tin  blacking 
box  covers  may  be  used  instead  of  platinum  dishes. 

Ash.  —  Ignite  the  platinum  dish  containing  the  residue  from 


ANALYTICAL   METHODS 


141 


the  preceding  determination  at  a  low  red  heat  until  the  ash  is 
white  or  of  a  uniform  light  gray  color.  This  may  be  done  in  a 
mufHe  furnace  at  a  temperature  not  exceeding  about  •600°  C, 
or  over  a  burner  carefully  regulated  so  that  the  dish  is  nowhere 
heated  above  the  slightest  visible  redness. 

The  ash,  after  weighing,  may  be  tested 
for  boric  acid  or  carbonates  as  described 
on  page  154. 

Fat.  —  (a)  Adams'  Paper  Coil  Method. 
Roll  a  strip  of  fat-free  blotting  paper  * 
about  22  inches  long  and  2^  inches  wide, 
into  a  loose  coil  and  fasten  it  by  a  bit 
of  wire.  Hold  the  coil  in  one  hand  and 
slowly  run  on  to  the  upper  end  of  it  ex- 
actly 5  c.c.  of  milk  from  a  pipette.  If 
preferred,  about  5  grams  of  milk  may 
be  weighed  quickly  in  a  small  beaker, 
and  one  end  of  the  coil  introduced  so  as 
to  absorb  the  milk,  care  being  taken  to 
absorb  it  as  nearly  completely  as  possible. 
The  beaker  is  then  quickly  re-weighed. 

Place  the  coil,  after  charging  with  the 
milk,  dry  end  downward,  in  the  water 
oven  and  dry  it  for  two  hours,  then 
extract  it  for  at  least  two  hours  in  a 
Soxhlet  extractor  as  shown  in  Fig.  i 
Use  about  100  c.c.  of  either  petroleum; 
ether  or  anhydrous  ethyl  ether  and  weigh 
the  flask  to  the  nearest  milligram.  At 
the  end  of  this  time  disconnect  the  appa- 
ratus when  the  extractor  is  nearly  full  of  ether,  thus  recovering 
a  large  portion  of  the  solvent,  and  evaporate  the  remainder 
{away  from  a  flame),  conveniently  by  the  electric  heater,  using 
suction.    Dry  the  fat  to  constant  weight  in  the  water-oven.    In 


Fig.  II. 


*  Schleicher  and  Schiill  make  suitable  strips  which  can  be  obtained  from  dealers 
in  chemical  suppHes,  or  the  strips  may  be  previously  prepared  in  the  laboratory 
from  thick  filter  paper  and  e.xtracted  with  ether  before  using. 


142  AIR,   WATER,  AND   FOOD 

drying  the  extracted  fat  it  may  be  heated  for  two  hours  the 
first  time,  then  in  one  hour  periods  until  the  loss  of  weight  is 
not  over  a  milligram. 

Notes.  —  The  only  part  of  the  method  due  to  Adams  is  the 
drying  of  the  milk  on  porous  paper.  This  is,  however,  of  great 
importance  since  the  absorbent  paper  exercises  a  selective 
action  on  the  constituents  of  milk  so  that  the  fat  is  left  on  the 
surface  of  the  paper,  mixed  with  only  about  one-third  of  the 
non-fatty  solids,  and  hence  is  more  easily  extracted;  further, 
owing  to  the  greatly  increased  surface  exposed,  the  extraction 
of  the  fat  is  practically  complete  in  a  comparatively  short  time. 

Ethyl  ether  is  the  solvent  commonly  employed  but  care  should 
be  taken  that  it  is  anhydrous,  otherwise  small  amounts  of  milk 
sugar  will  be  extracted.  For  this  reason  petroleum  ether  is 
to  be  preferred  as  a  solvent,  although  its  action  is  considerably 
slower  than  that  of  the  other. 

The  Adams  method  is  probably  the  most  accurate  for  fat  de- 
termination in  milk,  but  in  actual  practice  is  not  used  so  much 
as  the  more  rapid  centrifugal  methods. 

(b)  Babcock  Method.  —  Measure  17.6  c.c.  of  the  milk  from  a 
pipette  into  the  graduated  test  bottle;  add  17.5  c.c.  of  sulphuric 
acid  (sp.  gr.  =  1.825)  pouring  it  in  slowly  so  as  to  form  a  layer, 
beneath  the  milk.  After  the  acid  has  thus  been  added  to  all  the 
bottles  mix  the  milk  and  acid  thoroughly  by  a  rotary  motion, 
avoiding  the  spurting  of  the  liquid  into  the  neck  of  the  bottle. 
Place  the  bottles  in  opposite  pockets  of  the  centrifuge  in  even 
numbers  and  whirl  them  for  five  minutes  at  the  proper  speed. 
The  correct  speed  varies  from  1000  revolutions  per  minute  for 
a  lo-inch  wheel  to  700  for  one  of  24  inches  diameter.  Then  re- 
move the  bottles  and  add  hot  water  up  to  the  necks,  after  which 
whirl  them  again  for  one  minute.  Again  add  hot  water  until 
the  fat  rises  nearly  to  the  top  of  the  graduations.  Whirl  again 
for  one  minute.  Then  measure  the  length  of  the  column  of  fat 
by  a  pair  of  dividers,  the  points  being  placed  at  the  extreme 
lunits  of  the  column,  the  fat  being  kept  warm,  if  necessary,  by 
standing  the  bottles  in  water  at  60°  C.     If  now  one  point  of  the 


ANALYTICAL   METHODS 


143 


dividers  is  placed  at  the  o  mark  of  the  scale  on  the  bottle  used, 
the  other  will  indicate  the  per  cent  of  fat  in  the  milk. 

Notes.  —  Methods  based  on  centrifugal  separation  of  the  fat, 
of  which  the  Babcock  method  is  the  pioneer,  are  by  far  the  most 
rapid  and  convenient  for  general  use.  They  have  practically  re- 
placed the  more  tedious  extraction  methods  and  are  universally 
employed  in  creameries  and  milk  depots. 

When  the  acid  and  milk  are  mixed  the  mixture  becomes  hot 
and  turns  dark  colored  on  account  of  the  charring  of  the  milk 
sugar.  The  casein  is  first  precipitated  and  then  dissolved. 
The  retarding  effect  of  the  milk  serum  solids  being  thus  elimi- 
nated, the  fat  globules  are  free  to  collect  in  a  mass. 

The  fat  obtained  should  be  of  a  clear,  golden  yellow  color,  and 
distinctly  separated  from  the  acid  solution  beneath  it.  If  the 
fat  is  light-colored  or  whitish,  often  with  a  layer  of  white  par- 
ticles beneath  it,  it  generally  indicates  that  the  acid  is  too  weak 
or  that  the  milk  was  too  cold  when  the  acid  was  added.  A 
dark-colored  fat  with  a  sub-stratum  of  black  particles  indicates 
that  the  acid  is  too  strong.  The  best  results  will  be  obtained 
by  the  use  of  acid  of  the  strength  noted  above. 

The  capacity  of  the  graduated  neck  of  the  bottle  between  the 
o  and  10  marks  is  2  c.c.  The  specific  gravity  of  warm  milk  fat 
is  0.9,  hence  2  c.c.  will  weigh  1.8  grams  or  one-tenth  of  the 
weight  of  17.6  c.c.  of  milk  (approximately  18  grams).  The 
measurement  of  the  extreme  limits  of  the  column  of  fat,  rather 
than  to  the  upper  meniscus,  is  to  correct  for  the  small  amount  of 
fat,  0.1  to  0.2  per  cent,  that  remains  in  the  acid  solution. 

Milk  which  has  been  preserved  with  formaldehyde  usually  re- 
quires a  longer  time  and  more  vigorous  shaking  to  dissolve  the 
curd,  on  account  of  the  hardening  action  of  this  preservative  on 
the  coagulated  casein.  It  is  often  advantageous  to  stand  the 
bottles  in  water  at  60°  C.  for  a  time  before  whirling.  Samples 
containing  formaldehyde  will  usually  give  a  violet  color  when 
the  acid  is  added  to  the  milk. 

(c)  Gottlieb  Method.*  —  With  a  pipette  place  5  c.c.  of  milk 
in  a  50-c.c.  glass  stoppered  cylinder  and  add  the  following  re- 

*  Rose:  Z.  angew.  Chem.,  iSSS,  lOO;   Gottlieb:  LaitJw.  Vers.  Stat.,  iSg2,  6. 


144 


AIR,  WATER,  AND   FOOD 


agents,  being  careful  to  add  them  in  the  order  given  and  to 
shake  the  stoppered  cyhnder  thoroughly  after  the  addition  of 
each  reagent:  i  c.c.  of  ammonia  (sp.  gr.  =  0.96),  5  c.c.  of  alcohol, 
12.5  c.c.  of  ethyl  ether,  and  12.5  c.c.  of  petroleum  ether.  Let 
the  cylinder  stand  until  the  lower  layer  is  free  from  bubbles  — 
several  hours  if  necessary.  Transfer  the  upper  layer  to  a  tared 
flask  by  means  of  an  arrangement  similar  to  a  wash-bottle, 
as  shown  in  Figure  12.  Adjust  the  sliding  tube  until  the  end 
rests  just  above  the  junction  of  the  two  lay- 
ers, then  by  gently  blowing  force  out  the 
upper  layer  into  the  flask.  Repeat  the  ex- 
traction, using  10  c.c.  each  of  ethyl  ether  and 
petroleum  ether  and  blowing  it  off  into  the 
flask  as  before.  Distill  off  the  solvent  and 
dry  the  residual  fat  to  constant  weight  in 
the  water  oven.  Dissolve  the  weighed  fat 
in  a  Uttle  petroleum  ether.  If  a  residue 
is  found,  due  to  a  trace  of  the  aqueous  layer 
which  was  blown  off  with  the  ether,  wash  it 
several  times  in  the  flask  by  careful  decanta- 
tion  with  petroleum  ether.  Finally  dry  and 
weigh  the  flask  and  residue  and  deduct  from 
the  previous  weight.  The  difference  is  the 
weight  of  purified  fat. 
Notes.  —  All  of  the  successful  methods  for  determining  the  fat 
by  direct  extraction  from  the  milk  itself  involve  the  complete  or 
partial  solution  of  the  casein.  In  the  Gottlieb  method  the 
casein,  precipitated  from  the  milk  in  very  finely  divided  form  by 
the  alcohol,  is  dissolved  by  the  ammonia.  The  fat  is  dissolved 
by  the  ethyl  ether  and  the  addition  of  petroleum  ether  is  to 
render  less  soluble  the  milk  sugar  or  other  non-fatty  solids 
which  would  be  dissolved  by  ethyl  ether  alone. 

The  method,  while  apphcable  to  whole  milk,  is  especially 
valuable  in  determining  fat  in  such  products  as  skim  milk  or 
buttermilk  which  are  low  in  fat.  In  such  cases  it  is  better  to 
use  ID  c.c.  of  milk  and  double  the  quantity  of  reagents. 


ANALYTICAL   METHODS  145 

Milk  Sugar. —  The  sugar  in  milk  is  most  readily  determined 
by  its  reducing  action  on  P'chling's  solution. 

Munson  and  Walker  Method.*  —  Directions.  —  Measure  25 
c.c.  of  milk  into  a  500-c.c.  graduated  flask.  Add  about  400  c.c. 
of  water,  10  c.c.  of  copper  sulphate  solution,!  then  35  c.c.  of 
tenth-normal  sodium  hydroxide  (or  an  equivalent  cjuantity  of  a 
stronger  solution)  and  make  up  to  500  c.c.  Mix  thoroughly 
and  filter  through  a  dry  filter. 

In  a  No.  3  beaker  mix  25  c.c.  of  the  Fehhng's  copper  sulphate 
solution  and  25  c.c.  of  the  alkaline  tartrate  solution.  Add  50 
c.c.  of  the  milk  sugar  solution,  prepared  as  above,  cover  the 
beaker  with  a  watch  glass,  and  heat  it  upon  wire  gauze.  Reg- 
ulate the  flame  so  that  boiling  shall  begin  in  four  minutes,  and 
continue  the  boiling  for  exactly  two  minutes. 

Filter  the  cuprous  oxide  without  delay  through  asbestos  in 
a  weighed  Gooch  crucible,  wash  it  with  hot  water  until  free 
from  alkali,  pour  out  the  hot  filtrate,  then  wash  with  10  c.c. 
of  alcohol  and,  finally,  with  10  c.c.  of  ether.  Dry  the  crucible 
for  30  minutes  at  the  temperature  of  boiling  water  and  weigh. 
Find  the  milligrams  of  lactose  monohydrate  corresponding  to 
the  weight  of  cuprous  oxide  from  Table  XII  on  page  221  and 
calculate  the  percentage  present  in  the  milk. 

Notes.  —  Before  the  lactose  can  be  determined  by  Fehling's 
solution  the  protein  and  fat  must  first  be  removed.  This  is 
done  by  the  precipitation  with  copper  hydroxide,  the  fat  being 
carried  down  mechanically  by  the  precipitated  protein.  The 
addition  of  alkali  should  be  such  that  a  slight  excess  of  copper 
still  remains  in  solution,  since  an  excess  of  alkali  will  prevent 
the  precipitation  of  part  of  the  protein.  The  quantity  stated 
in  the  procedure  is  correct  for  most  milks. 

On  account  of  the  considerable  dilution  of  the  sample,  the  vol- 
ume of  the  precipitated  protein  and  fat  need  not  be  considered. 

The  general  principle  upon  which  all  these  methods  depend 

*  /.  Am.  Chem.  Soc,  igo6,  663;  1907,  541. 

t  69.28  grams  per  liter.  The  copper  sulphate  solution  used  in  the  Fehling  de- 
termination may  be  conveniently  employed. 


146  AIR,  WATER,  AND   FOOD 

is  based  on  the  fact  that  certain  sugars,  among  which  is  lactose, 
have  the  power  of  reducing  an  alkaline  solution  of  copper  to  a 
lower  state  of  oxidation  in  which  copper  is  separated  as  cuprous 
oxide.  The  copper  salt  which  is  found  to  give  the  most  dehcate 
and  reliable  reaction  is  the  tartrate.  The  two  solutions  which 
make  up  the  Fehling's  solution  are  best  preserved  separately, 
and  mixed  only  when  wanted  for  use,  as  otherwise  the  reducing 
power  of  the  solution  is  liable  to  change. 

The  amount  of  reduction  of  the  copper  salt  to  the  cuprous 
oxide  is  affected  by  the  rate  at  which  the  sugar  solution  is  added, 
the  time  and  degree  of  heating,  and  the  strength  of  the  sugar  so- 
lution; hence  the  necessity  for  adopting  a  definite  procedure 
and  for  taking  the  results  from  a  table  determined  by  exactly 
the  same  procedure  for  varying  amounts  of  the  sugar. 

The  asbestos  which  is  used  should  be  previously  boiled  in 
nitric  acid  and  then  in  dilute  sodium  hydroxide  and  thoroughly 
washed.  A  layer  about  a  centimeter  thick  should  be  used  in 
the  crucible,  and  a  "blank"  determination  made  with  the 
Fehling's  solution  should  not  show  a  change  in  weight  greater 
than  one-half  milligram.  After  the  precipitated  cuprous  oxide 
has  been  weighed  it  may  be  dissolved  in  hot  dilute  nitric  acid, 
and  the  asbestos  in  the  crucible  washed  and  dried  as  described, 
when  it  is  again  ready  for  use.  Do  not  remove  the  asbestos 
from  the  crucible. 

Proteins.  Determination  of  Total  Protein.  —  This  is  best  done 
by  the  Kjeldahl  method.  Weigh  5  grams  of  milk  into  a  Kjeldahl 
flask,  add  10  c.c.  of  concentrated  sulphuric  acid  and  three  drops 
of  mercury  and  carry  out  the  determination  as  described  on 
page  182. 

The  tendency  of  the  alkaline  solution  to  froth  during  the 
distillation,  which  is  especially  noticeable  with  milk,  can  be 
prevented  by  the  addition  of  a  piece  of  paraffin  the  size  of  a  pea. 
Multiply  the  per  cent  of  nitrogen  by  the  factor  6.38  to  obtain 
the  per  cent  of  protein. 

Separation  of  Casein  and  Albumin.  —  The  usual  method  of 
precipitating  the  casein  by  acid  at  a  temperature  below  the 


ANALYTICAL   METHODS  147 

coagulating  point  of  the  albumin,  while  capable  of  good  results, 
is  tedious  and  rather  unsatisfactory  except  after  considerable 
experience.  The  following  volumetric  method,  devised  by 
Van  Slyke  and  Bosworth  *  gives  results  of  almost  equal 
accuracy,  but  requires  much  less  time  and  skill. 

Measure  20  c.c.  of  the  well-mixed  milk  into  a  200-c.c.  grad- 
uated flask  and  add  about  80  c.c.  of  water.  Add  i  c.c.  of  phenol- 
phthalein  solution  and  tenth-normal  sodium  hydroxide  until  a 
faint  pink  color  remains  throughout  the  mixture  even  after  con- 
siderable shaking.     Avoid  an  excess  of  alkali. 

To  the  neutralized  diluted  sample,  which  should  be  at  a  tem- 
perature of  18°  C.  to  24°  C,  add  tenth-normal  acetic  acid  in 
.5-c.c.  portions,  shaking  vigorously  for  a  few  seconds  after  each 
addition.  After  thus  adding  25  c.c.  and  shaking,  the  mixture 
is  allowed  to  come  to  rest.  If  enough  acid  has  been  added,  the 
casein  separates  promptly  in  large,  white  flakes,  and  on  standing 
a  short  time,  the  supernatant  liquid  appears  clear,  not  at  all 
milky.  If  the  addition  of  25  c.c.  of  acid  is  insufiicient  to  sepa- 
rate the  casein  properly,  add  i  c.c.  more  of  acid  and  shake; 
continue  this  addition  of  acid  i  c.c.  at  a  time,  until  the  casein 
separates  promptly  and  completely  upon  standing  a  short  time. 
Note  the  number  of  c.c.  of  acid  used. 

After  the  casein  is  completely  precipitated  make  up  the  mix- 
tures to  the  200-c.c.  mark  with  water,  shake  thoroughly  and 
filter  through  a  dry  filter.  Filtration  should  be  rapid  and  the 
the  filtrate  quite  clear.  If  a  marked  turbidity  is  apparent  in 
the  filtrate,  a  new  sample  should  be  taken  and  the  process  re- 
peated, using  more  acid  than  before.  Titrate  100  c.c.  of  the 
filtrate  with  tenth-normal  sodium  hydroxide  and  phenolphtha- 
lein  to  a  pink  color  which  remains  throughout  the  solution  for 
thirty  seconds.  Subtracting  the  number  of  c.c.  of  sodium  hy- 
droxide from  one-half  the  c.c.  of  tenth-normal  acetic  acid  added 
will  give  the  c.c.  of  acid  required  to  precipitate  the  casein  for 

10  c.c.  of  milk,     (i  c.c.  of—    acetic  acid  =  o.II^I^    gms.  of 

casein.) 

*  /.  Ind.  Eng.  Clicm.,  igog,  768. 


148  AIR,   WATER,   AND   FOOD 

Calculation  of  Milk  Solids.  —  It  has  long  been  recognized  that 
in  normal  milk  the  constituents  are  present  in  a  fairly  constant 
ratio.  This  being  true,  it  should  be  possible,  having  deter- 
mined two  factors,  to  find  a  third  by  calculation,  or  at  least 
to  show  by  such  calculation  a  sufficient  variation  from  the 
normal  to  indicate  the  adulteration  of  the  sample.  For  ex- 
ample, given  the  lactometer  reading  and  fat,  to  calculate  the 
total  solids: 

L  =  the  lactometer  reading, 

5  =  increase  in  lactometer  reading  by  i  per  cent  sohds  not  fat, 
/  =  decrease  in  lactometer  reading  by  i  per  cent  fat, 
T  =  total  solids, 
S  =  per  cent  of  solids  not  fat, 
F  =  per  cent  of  fat. 

Then  L  =  Ss  -  Ff, 

Since  S  =  T  —  F 

L  =  {T-F)s-Ff, 

whence  T  =  ^  ~^  ^f  +  F. 

s 

The  uncertainty  of  the  calculation  lies  in  the  values  for  s  and/, 
which,  on  account  of  the  difference  in  solution  densities  of  the 
components  of  the  soHds  not  fat,  are  not  absolute  constants. 

Based  on  the  principle  just  stated,  various  formulae  have 
been  proposed  for  the  calculation  of  milk  solids.  One  of  the 
simplest  of  these  is  that  of  Hehner  and  Richmond  * 

T  =  — h  1.2F  +  0.14, 
4 

where  T  is  the  per  cent  of  total  solids,  L  the  reading  of  the  lac- 
tometer, and  F  the  fat. 

When  a  number  of  calculations  are  to  be  made,  Richmond's 
"Milk  Scale"  will  be  found  convenient.  This  is  an  instrument 
based  on  the  principle  of  the  slide-rule,  having  three  scales, 
two  of  which,  for  the  fat  and  the  total  soUds,  are  marked  on 

*  Analyst,  1888,  26;   i8g2,  170. 


ANALYTICAL  METHODS 


149 


the  body  of  the  rule,  while  that  for  the  lactometer  readings 
is  marked  on  the  sliding  part. 

A  similar  relation  has  been  worked  out  for  the  protein,  so 
that  if  a  constant  value  be  assumed  for  the  ash,  the  composition 
of  a  sample  may  be  determined  with  a  fair  degree  of  approxima- 
tion from  the  two  simple  determinations  of  specific  gravity  and 
Babcock  test. 

The  relation  between  the  protein  and  fat  has  been  expressed 
by  Van  Slyke*  as  P  =  0.4  (F  -  3)  +  2.8.  Similarly  Olsen  f 
has  proposed  the  following  formula  for  calculating  the  protein 
from  the  total  solids  (T.S.) : 

T.S. 
1-34 


P  =  T.S.  - 


These  values  will  naturally  be  most  nearly  correct  in  the  case 
of  normal  average  milk.  With  watered  or  skimmed  milk  they 
will  be  only  approximate. 

In  the  table  below  the  values  calculated  for  a  sample  are  com- 
pared with  those  actually  determined: 


Determination. 


Calculated  values. 


Lactometer  reading 

Fat  (Babcock) 

Total  solids 

Ash 

Proteins 

Milk  sugar 

Solids  not  fat 


12-95 

0.7  (assumed) 
j  3.12  (Van  Slyke) 
I  3.29  (Olsen) 

5.16 

915 


Examination  of  Milk  Serum.  —  The  most  variable  constitu- 
ents of  normal  milk  are  the  fat  and  protein,  especially  the  former; 
the  least  variable  are  the  ash  and  milk  sugar.  The  milk  serum, 
or  milk  from  which  the  fat  and  protein  have  been  removed,  is, 
therefore,  of  more  unifonn  composition  than  the  milk  itself, 
hence  better  suited  for  the  detection  of  adulteration  and  espe- 


*  /.  Am.  Chem.  Soc,  igoS,  1182. 
t  /.  Ind.  Eng.  Chem.,  iQog,  253. 


150  AIR,   WATER,   AND   FOOD 

cially  of  added  water.  The  serum  may  be  prepared  by  adding 
to  the  milk  some  suitable  precipitant  of  the  protein,  as  calcium 
chloride,  acetic  acid  or  copper  sulphate.  The  clear  liquid  after 
filtration  may  be  examined  for  its  content  of  dissolved  solids, 
its  specific  gravity  or  most  conveniently  by  the  immersion 
refractometer. 

The  Copper  Sulphate  Method. '^  —  Dissolve  72.5  grams  of 
crystallized  copper  sulphate  in  water  and  dilute  to  a  liter.  This 
solution  should  be  adjusted,  if  necessary,  so  that  it  will  refract  at 
36  degrees  on  the  scale  of  the  immersion  refractometer  at  20°  C. 
or  have  a  specific  gravity  of  1.0443  ^^  20°  C.  compared  with 
water  at  4°  C.  To  one  volume  of  the  copper  solution  add 
four  volumes  of  milk,  shake  well  and  filter.  The  filtrate  will 
usually  be  clear  after  the  first  few  drops  have  passed  through. 
On  the  clear  filtrate  either  the  refraction  at  20°  C,  the  specific 

— ^ )  or  the  total  solids  may  be  determined. 

Notes. — Examination  of  the  copper  serum  from  150  samples  of 
known  purity  milk  gave  refractions  varying  from  36.1  to  39.5, 
while  the  total  solids  of  the  same  samples  showed  a  range  from 
17.17  percent  to  10.40  per  cent  and  the  fat  varied  from  7.7  per 
cent  to  2.45  per  cent. 

The  minimum  values  for  the  copper  serum  of  normal  milk 
are  36  degrees  for  the  refraction  at  20°  C,  1.0245  for  the  specific 

gravity  \-^]  and  5.28  per  cent  for  total  solids. 

If  the  milk  is  already  soured,  it  may  be  filtered  and  similar 
determinations  made  on  the  natural  sour  serum,  which  for  un- 
watered  milk  should  not  refract  below  38.3  or  have  a  specific 

gravity  at 5-^  below  1.0229. 

4 

SPECIAL   TESTS   FOR   ADULTERANTS 

Cane    Sugar.  —  Cane  sugar   may  be  present    in  milk  from 
diluted  condensed  milk  used  to  eke  out  the  supply  or  may  be 
present  from  calcium  saccharate,  added  as  a  thickening  agent. 
*  Lythgoe:  Ann.  Rpt.  Mass.  Bd.  Health,  1908,  594. 


ANALYTICAL  METHODS  151 

It  is  evident  that  any  considerable  amount  which  had  been 
added  could  be  detected  by  the  taste. 

To  detect  the  presence  of  cane  sugar  boil  about  10  c.c.  of  the 
milk  with  o.i  gram  of  resorcin  and  i  c.c.  of  strong  hydrochloric 
acid  for  five  minutes.  The  liquid  will  be  colored  rose-red  if 
cane  sugar  is  present.  The  color  produced  by  heating  should 
not  be  confused  with  the  pink  color  which  may  appear  in  the 
cold  if  the  milk  contain  certain  coal-tar  colors. 

A  similar  test  is  the  reduction  of  ammonium  molybdate.  As 
recommended  by  Cotton  *  10  c.c.  of  the  milk  are  mixed  with 
0.5  gram  of  powdered  ammonium  molybdate  and  10  c.c.  of  dilute 
(i  to  10)  hydrochloric  acid  are  added.  In  another  tube  10  c.c. 
of  milk  known  to  be  free  from  sucrose  are  smiilarly  treated  and 
the  tubes  placed  in  a  water-bath,  the  temperature  of  which  is 
gradually  raised  to  about  80°  C.  If  sucrose  is  present,  the 
milk  will  gradually  turn  deep  blue,  while  genuine  milk  remains 
unchanged  unless  the  temperature  approaches  the  boiling  point. 
Cotton  states  that  the  reaction  will  detect  as  little  as  i  gram 
of  cane  sugar  in  a  liter  of  milk. 

Note.  —  Both  of  these  tests,  although  used  to  detect  cane 
sugar,  are  in  reahty  tests  for  levulose,  formed  in  this  case  by 
the  partial  inversion  of  the  sucrose. 

Preservatives.  —  The  preservatives  most  commonly  employed 
in  milk  are  formaldehyde,  boric  acid  or  borax,  and  mixtures  of 
the  two,  and  possibly  hydrogen  peroxide  and  fluorides.  Sali- 
cylic acid  and  sodium  benzoate,  although  largely  used  in  some 
other  classes  of  food  materials,  have  been  reported  very  rarely 
as  present  in  milk. 

Formaldehyde.  —  This  is  the  ideal  preservative  for  milk, 
being  readily  used  and  by  far  the  most  efficient.  Quantities 
which  give  a  proportion  in  the  milk  of  from  i  in  10,000  parts 
to  I  in  50,000  are  ordinarily  employed.  Such  an  amount  will 
suffice  to  preserve  the  milk  for  from  24  hours  to  several  days. 
Larger  quantities,  such  as  i  part  in  3000,  will  preserve  the  milk 
for  months.     These  large  amounts,  however,  would  be  more  or 

*  /.  Pharm.  Cliim.,  iSgj,  362. 


152  AIR,   WATER,   AND   FOOD 

less  apparent  by  the  taste  or  odor.  A  tabular  statement  show- 
ing the  efficiency  of  formaldehyde  in  preserving  milk  as  com- 
pared with  boric  acid,  borax  and  sodium  carbonate  will  be  found 
in  Leach's  Food  Analysis. 

Several  of  the  best  tests  for  detecting  formaldehyde  are  de- 
scribed below.  These  may  be  applied  directly  to  lo  c.c.  of  the 
milk,  or  as  suggested  in  the  gallic  acid  test,  a  larger  quantity, 
25  to  100  c.c,  may  be  distilled  and  the  test  applied  to  the  first 
portion  of  the  distillate. 

(i)  When  the  sulphuric  acid  is  added  to  the  milk  in  making 
the  Babcock  test  for  fat,  a  bluish-violet  ring  will  be  noticed 
at  the  junction  of  the  two  liquids  when  formaldehyde  is  present. 
One  part  of  formaldehyde  in  200,000  parts  of  milk  can  be  de- 
tected by  this  test,  but  it  fails  when  the  formaldehyde  amounts 
to  0.5  per  cent.  The  test  is  more  delicate  if  the  sulphuric  acid 
contains  a  trace  of  ferric  chloride. 

(2)  To  10  c.c.  of  milk  in  a  small  porcelain  dish  add  an  equal 
volume  of  hydrochloric  acid  (1.20  sp.  gr.).  Add  one  drop  of 
ferric  chloride  solution  and  heat  the  dish  with  a  small  flame, 
stirring  vigorously,  until  the  contents  are  nearly  boiling. 
Remove  the  flame  and  continue  the  stirring  for  two  or  three  min- 
utes, then  add  about  50  c.c.  of  water.  The  presence  of  formal- 
dehyde will  be  shown  by  a  violet  color  which  appears  in  the 
particles  of  the  precipitated  casein,  the  depth  of  color  depending 
on  the  amount  of  formaldehyde  present.  The  color  should 
be  observed  carefully  at  the  moment  of  dilution.  This  test 
readily  shows  the  presence  of  one  part  of  formaldehyde  in 
250,000  parts  of  milk,  if  fresh. 

(3)  Gallic  Acid  Test*  —  This  test  has  been  found  by  Shermanf 
to  be  much  more  delicate  than  either  of  the  preceding  tests. 
25  to  50  c.c.  of  the  milk  should  be  acidulated  with  phosphoric 
acid  and  distilled.  To  the  first  5  c.c.  of  the  distillate  add  0.2 
to  0.3  c.c.  of  a  saturated  solution  of  gallic  acid  in  pure  ethyl 

*  Barbier  and  Jandrier:  Ann.  Chint.  anal.,  i,  325;  Mulliken  and  Scudder:  Am. 
Chetn.  J.,  igoo,  444. 

t  /.  Am.  Chem.  Soc,  1905,  1499- 


ANALYTICAL   METHODS  1 53 

alcohol  and  pour  it  cautiously  down  the  side  of  an  inclined  test 
tube  containing  3-5  c.c.  of  pure  concentrated  sulphuric  acid. 
If  fonnaldehvdc  is  present  a  green  zone  is  formed  at  the  junction 
of  the  two  layers,  gradually  changing  to  a  pure  blue  ring. 

The  delicacy  of  the  test  is  about  one  part  of  formaldehyde  in 
500,000  parts  of  milk. 

Notes.  —  It  should  be  borne  in  mind  that  when  small  amounts 
of  formaldehyde  are  added  to  milk  the  ordinary  tests  will  show 
the  presence  of  the  preservative  for  only  a  short  time.  For 
example,  it  has  been  shown  by  Williams  and  Sherman  *  that 
when  formaldehyde  was  added  to  milk  in  the  proportion  of  i  part 
to  100,000  only  a  faint  test  was  given  after  48  hours  standing; 
and  that  the  preservative  had  entirely  disappeared  in  from  three 
to  five  days.  This  is  due  to  the  gradual  formation  of  conden- 
sation products  of  the  formaldehyde  with  the  proteins  of  the  milk 
which  do  not  respond  to  the  usual  reaction.  In  such  a  case,  it  is 
better  to  distill  the  milk  as  directed  and  apply  the  test  with 
gallic  acid  to  the  distillate.  The  test  is  thus  made  more  delicate, 
so  that  the  preservative  may  still  be  shown  when  the  simpler 
tests  have  failed. 

Another  possible  contingency  is  that  some  substance  may  be 
added  with  the  formaldehyde  which  will  interfere  with  the  tests 
for  its  detection.  Both  hydrogen  peroxide  and  nitrites  prevent 
the  reaction  of  formaldehyde  in  the  usual  tests  and  preserva- 
tives are  on  the  market  which  are  mixtures  of  fonnaldchyde 
with  hydrogen  peroxide  or  a  nitrite.  The  sulphuric  acid  test 
and  the  hydrochloric  acid-ferric  chloride  test  can  be  used  to 
show  the  formaldehyde  in  the  presence  of  considerably  larger 
quantities  of  nitrites  by  first  removing  the  latter.  Add  to  10  c.c. 
of  the  milk  i  c.c.  of  a  10  per  cent  solution  of  urea,  then  2  c.c. 
of  dilute  (i  :4o)  sulphuric  acid  and  immerse  the  test  tube  in  boil- 
ing water  for  two  minutes.  Cool  and  carry  out  the  test  as  usual. 
The  reaction  between  the  urea  and  the  nitrous  acid  may  be 
expressed : 

CO  (NHo)2  +  2  HXO,  =  COo  +  2  No  -t-  3  H.O. 

*  /.  Am.  Clicm.  Soc,  190 j,  1497. 


154  AIR,  WATER,  AND   FOOD 

Boric  Acid  or  Borax.  —  Make  25  c.c.  of  the  milk  distinctly 
alkaline  with  lime  water  and  evaporate  to  dryness  on  the  water- 
bath.  Char  the  residue  over  a  flame  but  do  not  necessarily 
heat  it  until  white.  Digest  the  residue  with  15-20  c.c.  of  water 
and  add  hydrochloric  acid  (1.12)  until  the  mixture  is  faintly 
acid  to  litmus  paper.  Filter,  and  add  i  c.c.  of  acid  in  excess. 
Place  a  strip  of  turmeric  paper  in  the  solution  and  evaporate  to 
dryness  on  the  water-bath.  If  boric  acid  or  borates  are  present, 
the  paper  takes  on  a  peculiar  red  color,  which  is  changed  by 
ammonia  to  a  dark  blue-green,  but  is  restored  by  acid.  Excess 
of  hydrochloric  acid  should  be  avoided,  as  it  turns  the  paper  a 
dirty  green  when  evaporated.  This  test  can  also  be  applied 
to  the  hydrochloric  acid  solution  of  the  ash. 

Sodium  Carbonate.  —  Detected  in  the  milk-ash,  as  on  page 
141.  If  effervescence  occurs,  test  the  original  milk  with  rosolic 
acid  as  follows:  Mix  10  c.c.  of  milk  with  an  equal  volume  of 
alcohol,  and  add  a  few  drops  of  a  one  per  cent  solution  of  rosolic 
acid.  The  presence  of  sodium  carbonate  is  indicated  by  a  more 
or  less  distinct  pink  coloration.  A  comparative  test  should  be 
made  at  the  same  time  with  milk  known  to  be  pure. 

Salicylic  and  benzoic  acids.  —  If  it  is  desired  to  test  for  these, 
the  following  method  may  be  employed.  To  25  c.c.  of  milk  add 
100  c.c.  of  water  and  precipitate  the  proteins  and  fat  with  copper 
sulphate  and  sodium  hydroxide,  as  described  on  page  145. 
Filter  and  add  to  the  filtrate  5  c.c.  of  concentrated  hydro- 
chloric acid.  Extract  with  ether  and  proceed  as  outlined  on 
page  196. 

Coloring  Matter.  —  The  object  in  adding  coloring  matter  to 
milk  is  in  general  to  disguise  the  bluish  appearance  of  skimmed 
or  watered  milk.  For  this  reason  it  is  rather  unusual  to  find 
added  color  in  the  case  of  milk  which  is  of  standard  quality, 
although  such  cases  have  been  reported. 

Formerly  the  chief  color  used  was  annatto,  a  reddish-yellow 
coloring  matter  obtained  from  the  seeds  of  Bixa  Orellana,  a 
shrub  growing  in  South  America  and  the  West  Indies.  A  solution 
of  the  color  in  very  dilute  alkali  is  employed.     More  recently 


ANALYTICAL  METHODS  1 55 

various  coal-tar  dyes  and  even  caramel  have  been  used.  The 
latter  is,  perhaps,  not  so  likely  to  be  found,  because  its  color 
is  too  brown  and  not  enough  yellow  to  give  the  desired  creamy 
appearance  to  the  milk  which  is  so  easily  obtained  with  annatto. 
The  coal-tar  colors,  especially  mixtures  of  yellow  and  orange 
azo  dyes,  give  very  good  results. 

Leach  *  has  suggested  a  general  scheme  for  the  identification 
of  these  colors  in  milk,  which  with  some  modifications  which 
experience  in  the  writer's  laboratory  has  shown  to  be  helpful 
in  detecting  annatto  especially,  is  given  below. 

Procedure.  —  Place  about  100  c.c.  of  the  milk  in  a  small 
beaker,  add  3-4  c.c.  of  25  per  cent  acetic  acid  (sp.  gr.  =  1.04), 
stir  thoroughly  and  allow  the  beaker  to  stand  quietly  on  the 
water-bath  for  about  ten  minutes,  the  casein  being  thus  sepa- 
rated as  a  compact  cake.  Decant  off  the  whey,  squeezing  the 
curd  as  dry  as  possible  with  a  spatula.  Transfer  the  curd  to 
a  flask,  cover  it  with  ether,  stopper  tightly,  and  shake  the  flask 
violently  in  order  to  break  up  the  curd  as  much  as  possible. 
Let  it  stand  for  several  hours,  preferably  over  night. 

Pour  off  the  ether,  which  contains  the  annatto,  and  evap- 
orate {away  from  a  flame)  until  no  odor  of  ether  remains.  Add 
5  c.c.  of  water  and  then  dilute  sodium  hydroxide  until  the  mix- 
ture, after  thorough  stirring  with  a  glass  rod,  is  faintly  alkaline 
to  litmus  paper,  and  filter  through  a  wet  filter.  If  annatto  is 
present  it  will  permeate  the  filter  and  give  it  an  orange-brown 
color  which  may  readily  be  seen  if  the  filter  is  removed  from  the 
funnel  and  the  fat  washed  off  under  the  tap.  Its  presence  may 
be  confirmed  by  touching  the  colored  portion  of  the  paper  with 
a  drop  of  stannous  chloride,  which  gives  a  pink  color  with  annatto. 

After  pouring  off  the  ether  examine  the  milk-curd  for  caramel 
or  coal-tar  color.  If  the  curd  is  left  white,  neither  of  these 
colors  is  present.  If  caramel  has  been  used,  the  curd  will  be  of 
a  pinkish-brown  color;  if  the  color  is  due  to  the  coal-tar  dye, 
the  curd  will  have  a  yellow  or  orange  tint.  If  now  some  con- 
centrated hydrochloric  acid  is  poured  over  the  curd,  the  color 
*  J.  Am.  Cfiem.  Soc,  igoo,  207. 


156  AIR,   WATER,   AND   FOOD 

will  change  immediately  to  a  bright  pink  with  the  coal-tar  colors 
ordinarily  used. 

Notes.  —  When  the  milk  is  curdled  by  the  acid,  any  added  color 
is  carried  down  by  the  curd.  When  this  is  subsequently  treated 
with  ether  the  fat  and  annatto  are  dissolved,  leaving  any  cara- 
mel or  coal-tar  color  still  in  the  curd.  Since  the  detection 
of  the  two  latter  colors  may  depend  upon  recognizing  color  in 
the  curd,  this  should  always  be  compared  with  the  curd  prepared 
in  the  same  manner  from  a  sample  of  milk  known  to  be  free  from 
color. 

The  ordinary  tests  for  caramel  as  used  to  show  its  presence 
in  distilled  liquors  or  vanilla  extract  are  not  sufficiently  delicate 
to  detect  the  extremely  small  quantity  which  suffices  to  impart 
the  desired  shade  of  color  to  the  milk.  The  color  imparted  to 
the  curd,  however,  is  characteristic  and  readily  recognized. 

It  is  possible  that  coal-tar  dyes  may  be  used  which  do  not 
give  the  pink  reaction  with  hydrochloric  acid,  since  this  is  char- 
acteristic in  general  only  of  the  azo  class  of  dyes.  Even  in 
these  cases,  however,  the  orange  color  of  the  dye  is  readily  per- 
ceptible in  the  separated  curd. 

Milk  colored  with  an  azo  dye  may  occasionally  fail  to  show 
its  presence  if  the  sample  is  old  or  partly  decomposed  before 
being  tested.  This  has  been  shown  by  Blyth  *  to  be  due  to  the 
reduction  of  the  dye  by  nascent  hydrogen  produced  by  the  growth 
of  certain  anaerobic  organisms. 

Interpretation  of  Results.  —  Apart  from  the  addition  of 
foreign  ingredients,  such  as  colors  and  preservatives,  which  are 
detected  by  the  specific  tests  described,  the  most  common  forms 
of  adulteration  are  the  addition  of  water  and  the  removal  of 
cream.  By  reference  to  the  table  on  page  136,  it  will  be  seen 
that  on  account  of  the  variation  in  the  composition  of  unadul- 
terated cow's  milk  the  detection  in  all  cases  is  not  an  easy  prob- 
lem. The  variation  in  the  fat  content,  especially,  makes  it 
more  difficult  to  show  with  certainty  the  partial  removal  of 
cream  than  the  addition  of  water. 

*  Analyst,  1902,  146. 


ANALYTICAL   METHODS 


157 


This  is  well  shown  in  the  following  table  in  which  "^  "  is 
a  normal  milk,  "5"  the  same  milk  in  which  the  fat  has  been 
reduced  to  3.6  per  cent  by  adding  water  and  "C"  the  same  milk 
in  which  the  fat  has  been  reduced  to  3.6  per  cent  by  skimming. 


A 

B 

C 

Total  solids 

12.78 
4.00 
2.89 
5.00 
0.71 
8.78 

11-34 
3.60 
2.60 

4  50 
0.64 

7-74 

12.09 
3  60 

Fat 

Protein 

2.91 
4.98 
0.72 
8.6i 

Sugar 

Ash 

Solids  not  fat 

It  is  seen  that  in  sample  C  it  is  only  the  fat  that  has  been 
decreased  to  any  degree.  In  fact  there  is  nothing  in  the  figures 
given  for  C  to  indicate  in  any  way  that  the  sample  is  not  genuine 
milk,  while  in  B  the  soHds  not  fat  are  so  low  as  to  show  the  adul- 
teration quite  plainly. 

Composition  of  Milk  of  Known  Purity.  —  The  average  com- 
position of  milk,  together  with  the  usual  and  the  extreme  limits 
of  variation,  have  already  been  stated  on  page  136.  The  greater 
number  of  published  analyses  of  genuine  cows'  milk  have  been 
limited  to  determination  of  sohds,  fat  and  specific  gravity.  A 
more  detailed  study,  including  the  constants  of  the  copper 
serum,  will  be  found  in  the  following  table,*  which  includes  the 
analyses  of  33  samples  of  known  purity  milk  from  individual 
cows,  and  4  samples  of  herd  milk,  arranged  in  the  order  of  their 
percentage  of  total  solids. 

In  collecting  the  samples  milk  was  taken  from  the  heaviest 
milkers,  so  as  to  include  a  larger  proportion  of  low-grade  milk 
for  minimum  values.  None  of  the  milk  could  be  called  excbp- 
tionally  high  grade,  as  samples  were  not  collected  from  Jersey  or 
Guernsey  cows. 

Inspection  of  this  table  shows,  as  would  be  expected,  a  great 
variation  in  the  percentage  of  fat  in  the  individual  samples,  the 
highest  being  almost  100  per  cent  higher  than  the  minimum 
values.     The  solids  not  fat  are  seen  to  present  a  much   less 

*  Lythgoe:  Bull.  Mass.  Bd.  Health,  1910,  422. 


158  AIR,  WATER,   AND   FOOD 

variation,  and  as  Lythgoe  has  pointed  out,  this  variation 
is  due  very  largely  to  the  changes  in  protein  content,  the  milk 
sugar  and  ash  remaining  fairly  constant.  Upon  this  fact 
depends  the  special  value  of  an  examination  of  the  milk 
serum. 

In  some  cases  all  that  may  be  necessary  is  to  show  by  the 
analysis  that  the  milk  does  not  conform  to  the  legal  standard. 
In  certain  of  the  states,  however,  a  legal  distinction  is  made 
between  milk  which  is  simply  below  standard  and  milk  which  has 
been  actually  adulterated  by  skimming  or  watering.  It  is  there- 
fore of  importance  to  show  by  the  analysis  whether  water  has 
been  added  to  the  milk  directly  and  not  through  the  breed  or 
feed  of  the  cow. 

Detection  of  Watered  Milk.  —  Since  in  general  the  water  that 
has  been  added  is  no  different  from  the  water  already  present 
in  the  milk  it  is  evident  that  this  form  of  adulteration  can  be 
detected  only  by  showing  chemical  or  physical  changes  in  the 
milk  that  could  be  ascribed  only  to  the  addition  of  water.  Meth- 
ods have  been  proposed,  it  is  true,  based  on  differences  in  the 
added  water,  such  as  an  abnormally  high  amount  of  nitrates, 
which  might  have  been  derived  from  the  polluted  barnyard 
well,  but  these  methods  are  of  little  importance. 

(a)  Solids  Not  Fat.  —  Since  the  variation  in  proportion  of 
solids  not  fat  in  normal  milk  is  much  less  than  the  range  of 
total  solids  this  is  of  distinct  value  in  showing  added  water. 
Although  as  indicated  in  the  table  of  limiting  values  on  page  136, 
the  value  for  solids  not  fat  may  go  as  low  as  7.5  per  cent,  this 
is  rather  uncommon,  and  a  fairer  minimum  would  be  7.7  per 
cent.  A  value  below  7.7  per  cent  would  certainly  be  suspicious 
of  added  water  and  if  accompanied  by  correspondingly  low  values 
for  the  constants  of  the  serum  could  be  regarded  as  direct  evidence 
of  adulteration. 

(b)  Milk  Sugar.  —  As  suggested  by  Lythgoe,*  the  milk  sugar 
may  be  employed  to  even  greater  advantage  than  the  soHds  not 
fat  in  showing  adulteration.    Knowing  the  percentage  of  solids 

*  Loc.  cit. 


ANALYTICAL  METHODS 


159 


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AIR,   WATER,  AND   FOOD 


and  of  fat,  the  protein  may  be  calculated  by  the  formulae  given 
on  page  149.  Then  if  0.7  be  assumed  as  the  value  for  the  ash, 
the  milk  sugar  may  be  determined  by  subtracting  from  the 
total  solids  the  sum  of  the  other  constituents.  The  expression 
for  the  milk  sugar  would  then  become 

(i)  Milk  sugar  =  T.S.  -  {F -\-  [0.4  (7^  -  3)  +  2.8]  +  0.7). 

T.S. 


(2)  Milk  sugar  =  T.S.  -  (F + 


T.S. 


1-34. 


+  0.7). 


The  portion  of  the  formula  enclosed  in  brackets  is  the  calcu- 
lated protein  in  each  case.  In  the  case  of  pure  milk  the  formulas 
for  calculating  the  protein  will  give  very  similar  results,  but 
with  adulterated  milk  they  will  be  divergent,  the  difference, 
increasing  with  the  extent  of  adulteration.  In  the  case  of 
watered  milk  the  calculated  milk  sugar  will  be  too  low,  ordinarily 
falhng  below  4.2  per  cent,  while,  as  will  be  shown  later,  with 
skimmed  milk,  the  milk  sugar  will  be  too  high,  generally  above  4.8 
per  cent. 

(c)  Milk  Serum.  —  If  the  preliminary  calculation  indicates  a 
possibility  of  the  samples  being  watered  an  examination  of  the 
serum  should  be  made.  This  may  be  done  preferably  by  the 
copper  sulphate  method,  which  is  described  and  the  minimum 
values  for  pure  milk  stated  on  page  150.  The  following  table 
due  to  Lythgoe  shows  the  effect  of  systematic  watering  on  the 
composition  of  the  milk  and  the  constants  of  the  serum  in  the 
case  of  a  milk  which  was  above  the  average  in  solids  not  fat 
and  refraction. 

COMPOSITION  OF  A  SAMPLE  OF  MILK  SYSTEMATICALLY 
WATERED 


Added 

Solids 

(per 

cent). 

Fat  (per 
cent). 

Solids  not 
fat  (per 
cent). 

Copper  serum. 

water 

(per 

cent). 

Refrac- 
tion, 20°. 

specific 

gravity, 

20° 

4° 

Solids 

(per 

cent). 

0 
10 
20 
30 
40 
50 

13.18 

11.86 

10 -54 

9  23 

7.91 

6.59 

4.  20 
3.78 
3.36 
2.94 
2.52 
2.  10 

8.98 
8.08 
7.18 
6.  29 
5-39 
4-49 

38.5 
36.4 
34-4 
32.4 
30.6 
28.6 

I .0272 
I .0249 
1.0233 
I .0211 
I .0194 
I. 0174 

6.09 
5-57 
5-05 
4.56 
4. 10 
3-54 

ANALYTICAL  METHODS  l6l 

It  is  seen  that  each  5  per  cent  of  added  water  lowers  the 
refraction  by  one  scale  division,  hence  with  average  milk, 
refracting  below  38  degrees,  10  per  cent  of  added  water  could 
be  detected,  and  with  rich  milk  15  per  cent  can  usually  be 
found. 

Detection  of  Skimmed  Milk.  —  Watering  milk  does  not  in 
general  change  the  relation  of  the  various  constituents  to  one 
another,  since  these  are  all  reduced  in  the  same  proportion, 
but  removing  the  fat  does  change  these  ratios.  It  is  immaterial 
whether  the  milk  is  skimmed  by  the  actual  removal  of  some  of 
the  fat  or  whether  separator  skim  milk  is  added  to  normal  milk. 
In  either  case  the  resulting  product  will  have  its  fat  content 
largely  reduced,  while  the  proteins  and  sugar  suffer  but  little 
change.  In  normal  milk,  especially  in  the  mixed  milk  of  a  herd, 
the  percentage  of  fat  is  rarely  less  than  the  protein  (see  table, 
page  159).  In  5500  analyses  of  American  milks  compiled  by 
Van  Slyke,  with  a  fat  content  between  3  and  5  per  cent,  the 
average  amount  of  fat  was  3.92  per  cent  and  the  average  amount 
of  proteins  3.20  per  cent.  If  such  milk  be  skimmed  the  fat  may 
be  reduced  to  i  per  cent  or  even  to  o.i  per  cent  but  the  protein 
content  will  still  be  approximately  the  same  as  before.  In  the 
calculation  of  milk  sugar  by  the  formulae  given  on  page  160, 
the  same  effect  will  be  noticed,  that  is,  the  skimming  will 
lower  the  fat  or  the  soHds  to  a  greater  extent  than  the  protein. 
Hence  the  proteins  calculated  from  the  fat  or  total  solids  will 
be  too  low  and  the  calculated  milk  sugar  will  be  too  high.  For 
practical  purposes  the  limit  for  unskimmed  milk  may  be  set 
at  4.8  per  cent,  values  above  this  being  suspicious  of  skimmed 
milk. 

In  addition  to  this  preliminary  test,  the  milk  may  be  with 
certainty  declared  skimmed  if  the  fat  falls  below  2.2  per  cent, 
the  solids  not  fat  remaining  above  the  average  value  of  8.5 
per  cent.  If  the  fat  is  above  2.2  per  cent  and  below  3.5  per 
cent,  the  presence  of  skimmed  milk  may  be  confirmed  by  making 
a  KJeldahl  nitrogen  detennination  on  the  suspected  sample  and 
calculating  the  proteins  by  the  factor  6.38.     If  the  proteins 


l62  AIR,  WATER,  AND   FOOD 

exceed  the  fat,  as  stated  in  the  preceding  paragraph,  the  sample 
is  skimmed.  If,  however,  the  fat  is  above  3.5  per  cent,  this  pro- 
cedure will  no  longer  suffice,  since  the  proteins  rarely  exceed 
3.5  per  cent.  In  these  few  cases,  the  skimming  can  be  judged 
only  from  the  high  specific  gravity,  high  solids  not  fat  and  cor- 
respondingly low  fat. 

Specific  Gravity  of  Milk  Solids.  —  The  specific  gravity  of  the 
milk  solids  is  sometinies  used  to  show  skimming.  Fleisch- 
mann's  formula  for  calculating  this  is 

T.S. 
^  o    _  (100  X  Gr)  —  100 
Gr 

when  T.S.  =  the  total  solids  and  Gr  the  specific  gravity  of  the 
milk. 

Example.  —  A  sample  of  milk  contains  12.85  P^^  cent  of  milk 
solids  and  has  a  specific  gravity  of  1.031.  Required  the  specific 
gravity  of  the  milk  solids. 

i2.8t;  i2.8t;  , 

X  ^  =  =  I.'^OO. 

12  SS  ^^^°  ^   ^'^^^^   ~   ^°^         12.85-3.006 

1-031 

The  specific  gravity  of  the  solids  of  normal  milk  varies  be- 
tween 1.25  and  1.34.  It  is  not  changed  by  watering  the  milk, 
but  is  increased  by  removing  the  fat  or  adding  skimmed  milk. 
A  value  above  1.32  is  suspicious  while  a  specific  gravity  of  the 
milk  solids  above  1.40  is  regarded  as  conclusive  evidence  of 
skimming. 

BUTTER 

General  Statements.  —  Butter  consists  of  the  fat  of  milk, 
together  with  a  small  percentage  of  water,  salt,  and  curd.  The 
curd  is  made  up  principally  of  the  casein  of  the  milk.  These 
various  ingredients  are  present  in  about  the  following  propor- 
tions : 

Fat 78.00-90.0  per  cent;  average,  82  per  cent. 

Water 5.00-20.0  per  cent;  average,  12  per  cent. 

Salt 0.40-15.0  per  cent;  average,  5  per  cent. 

Curd o.ii-  5.3  per  cent;  average,  i  per  cent. 


ANALYTICAL  METHODS 


163 


The  fat  consists  of  a  mixture  of  the  glycericles  of  the  fatty 
acids.  The  characteristic  feature  of  butter-fat  is  the  extraor- 
dinarily high  proportion  of  the  glycerides  of  the  soluble  and 
volatile  fatty  acids  when  contrasted  with  other  fats. 

The  following  may  be  taken  as  the  probable  composition 
of  normal  butter-fat :  * 


Acid. 

Per  cent 
Acid. 

Per  cent 
Triglycerides. 

Dioxystearic 

I  .00 
32.50 

1.83 
38.61 

9.89 

2.57 
0.32 
0.49 
2.09 
5.45 

1 .04 

33.95 
1. 91 

40.51 
10.44 

2.73 
0.34 
0.53 
2.32 
6.23 

Oleic 

Stearic 

Palmitic 

Myristic 

Laurie 

Capric 

Caprylic 

Caproic 

Butyric 

Total 

94-75 

100.00 

According  to  this,  the  proportion  of  volatile  acids  in  butter 
(butyric,  caproic,  caprylic  and  capric  acids)  amounts  to  8.35  per 
cent.  The  amount  of  volatile  acid  in  lard,  for  example,  is  about 
0.1  percent. 

The  usual  examination  of  butter  consists  in  the  examina- 
tion of  the  butter-fat,  in  order  to  detect  the  presence  of  foreign 
fats.  Those  commonly  used  for  this  purpose  are  lard,  oleo- 
margarine, and  sometimes  butter  substitutes  containing  cocoanut 
oil. 

The  term  "oleomargarine"  is  usually  applied  to  a  mixture 
of  refined  lard,  "oleo  oil,"  which  is  mainly  the  olein  of  beef  fat, 
and  cottonseed  oil.  Ordinarily  a  small  proportion  of  butter 
is  added  and  the  product  is  generally  churned  with  milk. 

A  comparatively  recent  form  of  butter  substitute  which 
finds  extensive  use  in  some  sections  of  the  country  is  "  process," 
or  "renovated,"  butter.  The  raw  material,  or  "stock,"  used  for 
the  manufacture  of  this  consists  of  butter  which  cannot  be  sold 

*  Browne:  /.  Am.  Chem.  Soc,  iSgg,  807. 


164  AIR,  WATER,  AND   FOOD 

as  butter  either  because  of  deterioration  through  rancidity  or 
molding  or  because,  through  carelessness  on  the  part  of  the 
makers,  it  possesses  an  unattractive  appearance  or  flavor.  The 
chief  recruiting-ground  for  this  material  is  the  country  grocery 
store.  The  fat,  separated  from  the  curd  by  melting  and  settling, 
is  aerated  to  remove  disagreeable  odors  and  leave  it  nearly 
neutral.  This  is  then  emulsilied  with  fresh  milk  which  has 
been  inoculated  with  a  bacterial  culture,  and  the  whole  is  chilled, 
granulated,  and  churned.  The  butter  is  then  worked  and  packed 
for  market  in  the  usual  manner.  The  character  of  the  product 
has  much  im.proved  since  the  early  days  of  the  industry,  the 
best  grades  now  approximating  the  lower  grades  of  creamery 
butter. 

The  "aroma"  of  butter  seems  to  be  connected  with  the  decom- 
position produced  by  the  action  of  bacteria  on  the  casein  and 
the  small  amount  of  milk-sugar  that  is  present,  and  not  with 
any  change  in  the  fats;  there  is  no  evidence,  however,  that  any 
unwholesome  effect  is  produced  by  the  aroma-giving  organisms. 

The  rancidity  of  butter-fat  is  generally  considered  to  be 
due  to  decomposition  and  oxidation  of  the  fatty  acids,  espe- 
cially the  unsaturated  ones,  the  amount  of  change  depending 
on  conditions  of  light,  heat,  and  exposure  to  air. 

Analysis  of  Butter.  —  Apart  from  the  examination  of  the 
butter  fat  to  detect  the  addition  of  foreign  fats,  butter  itself 
is  often  analyzed  in  order  to  determine  variations  in  its  con- 
stituents from  the  normal,  or  the  addition  of  deleterious 
substances. 

The  Federal  standard  for  butter  describes  it  as  "the  clean, 
non-rancid  product  made  by  gathering  in  any  manner  the  fat 
of  fresh  or  ripened  milk  or  cream  into  a  mass,  which  also  con- 
tains a  small  portion  of  the  other  milk  constituents,  with  or 
without  salt,  and  contains  not  less  than  eighty-two  and  five- 
tenths  (82.5)  per  cent  of  milk  fat.  By  acts  of  Congress  approved 
August  2,  1886,  and  May  9,  1902,  butter  may  also  contain  added 
coloring  matter." 

The  determinations  usually  made   to  ascertain  whether  the 


ANALYTICAL  METHODS  1 65 

butter  is  of  standard  quality  arc  the  water,  fat,  ash,  curd,  and 
salt.  Of  these  the  first  four  can  be  made  on  the  same  weighed 
sample,  following  in  general  the  methods  recommended  by  the 
Association  of  Official  Agricultural  Chemists.* 

The  following  method  is  simpler  and  gives  results  comparable 
with  the  official  methods: 

Weigh  about  2  grams  of  butter  into  a  platinum  Gooch  cruci- 
ble, half-iilled  with  ignited  fibrous  asbestos,  and  dry  it  at  100°  C. 
to  constant  weight.  The  loss  in  weight  is  the  amount  of  water. 
Then  treat  the  crucible  repeatedly  with  small  portions  of  pe- 
troleum ether,  using  gentle  suction,  and  again  dry  it  to  constant 
weight.  The  difference  between  this  and  the  preceding  weight 
will  be  the  amount  of  fat.  Now  carefully  heat  the  crucible 
over  a  small  flame  or  in  a  muffle  until  a  light  grayish  ash  is 
obtained.  The  loss  in  weight  is  the  amount  of  curd,  and  the 
residual  increase  in  weight  over  that  of  the  crucible  and  asbestos 
is  the  ash.  If  desired,  the  salt  may  be  washed  out  of  the  ash 
and  determined  by  titration  with  silver  nitrate  after  neutraliz- 
ing the  solution  with  calcium  carbonate. 

Notes.  —  If  the  sample  for  analysis  is  to  be  taken  from  a 
considerable  quantity  of  butter,  great  care  must  be  taken  in 
sampling,  because  the  butter  is  usually  not  homogeneous  in 
composition  and  cannot  be  mixed  by  stirring.  The  best  plan 
is  to  take  a  fairly  large  sample  of  100  to  200  grams  or  more, 
melt  it  at  the  lowest  possible  temperature  in  a  jar  or  wide- 
mouthed  glass-stoppered  bottle  and  mix  by  \dolent  shaking. 
Then  cool  until  sufficiently  solid  to  prevent  the  separation  of  the 
fat  and  water,  taking  especial  care  to  shake  the  sample  thor- 
oughly during  the  cooling. 

Rapid  methods  for  the  determination  of  water  in  butter  have 
been  devised  by  Patrick  f  and  Gray  |  especially  for  the  exami- 
nation of  large  numbers  of  samples. 

Good  butter  should  in  general  contain  not  less  than  the  amount 

*  Bur.  ofCliem.,  Bull.  107  {Rev.),  p.  123. 
t  /.  .\»i.  Cliem.  Soc,  1007,  1126. 
t  Bur.  .\nimal  Ind.,  Circ.  icx3. 


1 66  AIR,   WATER,   AND   FOOD 

oi  fat  required  by  standard,  not  more  than  2.0  per  cent  of  curd, 
and  not  over  16  per  cent  of  water. 

5a//.  —  If  a  direct  detennination  of  salt  is  desired,  the  fol- 
lowing method,  although  tedious,  will  give  satisfactory  results: 

Weigh  10  grams  of  butter  in  a  small  beaker,  add  30  c.c.  of 

hot  water,  and  when  the  fat  is  completely  melted  transfer  the 

whole  to  a  separatory  funnel.     Shake  the  mixture  thoroughly, 

allow  the  fat  to  rise  to  the  top,  and  draw  off  the  water,  taking 

care  that  none  of  the  fat-globules  pass  the  stopcock.     Repeat 

the  operation  four  times,  using  30  c.c.  of  water  each  time.     Make 

the  washings  up  to  250  c.c,  mix  thoroughly,  and  titrate  25 

.        .  .       N     . 

c.c.  in  a  six-inch  porcelam  dish,  usmg  —  silver  nitrate  with 

20 

potassium  chromate  as  an  indicator. 

Preservatives.  —  About  50  grams  of  butter  are  mixed  with 
25  c.c.  of  chloroform  in  a  separatory  funnel,  100  c.c.  of  dilute 
(o.i  per  cent)  sodium  carbonate  solution  added,  and  the  whole 
mixed,  avoiding  violent  shaking.  After  the  separation  of  the 
layers,  which  may  be  greatly  aided  by  a  suitable  centrifuge, 
the  aqueous  layer  is  examined  for  preservatives,  especially  for 
boric,  benzoic  and  salicylic  acids,  by  the  methods  described  on 
pages  154  and  196. 

Colors.  —  No  methods  are  described  for  the  detection  of 
colors  in  butter  since  these,  being  allowed,  do  not  constitute 
an  adulteration.  If  it  be  desired  to  test  for  added  color  in  oleo- 
margarine, methods  may  be  found  in  Allen's  Commercial  Organic 
Analysis,  4th  Ed.,  Vol.  II,  or  in  Leach's  Food  Analysis. 

Examination  of  the  Fat.  —  The  fat  is  first  separated  from  the 
other  constituents  of  the  butter  so  that  it  may  be  weighed  out 
for  the  various  tests. 

Directions.  —  Melt  a  piece  of  butter,  about  two  cubic  inches, 
in  a  small  beaker  placed  on  top  of  the  water-bath  so  that  the 
temperature  shall  not  rise  above  50°  to  60°.  After  about  fifteen 
minutes  the  water,  salt,  and  curd  will  have  settled  to  the  bottom. 
(A  better  separation  may  be  secured  by  dividing  the  melted 
sample  equally  between  two  test-tubes  and  whirling  them  for 


ANALYTICAL  METHODS  167 

3  to  4  minutes  in  a  centrifugal  machine.)  Place  a  bit  of  absorb- 
ent cotton  in  a  funnel,  previously  warmed,  and  decant  off  the 
clear  fat  through  the  cotton  into  a  second  beaker,  taking  care 
that  none  of  the  water  or  curd  is  brought  upon  the  filter.  When 
the  filtered  fat  has  cooled  to  about  40°  place  a  small  pipette  in 
the  beaker  and  weigh  the  whole. 

By  means  of  the  pipette  the  desired  amount  of  fat  is  taken 
out,  the  pipette  replaced  in  the  beaker,  and  the  whole  again 
weighed.  The  difference  in  weight  gives  the  exact  amount 
of  fat  taken.  It  is  a  saving  of  time,  however,  if  several  por- 
tions are  to  be  weighed  out,  to  make  the  weights  one  after 
another,  so  that  one  weight  will  suffice  for  a  determination. 
Weigh  out  thus:  Two  portions  of  5  grams  each  into  250-c.c. 
round-bottomed  flasks  for  the  Reichert-Meissl  method,  one 
portion  of  2.5  to  3  grams  into  a  500-c.c.  beaker  for  Hehner's 
process,  two  portions  of  about  0.35  to  0.5  gram  each  into  300-c.c. 
glass-stoppered  bottles  for  determination  of  the  iodine  value. 
In  the  case  of  the  larger  portions,  weigh  only  to  the  nearest 
milligram. 

(i)  Reichert-Meissl  Number  for  Volatile  Fatty  Acids  —  Di- 
rections. —  To  the  fat  in  the  250-c.c.  flasks  add  2  c.c.  of  strong 
caustic  potash  (i  :  i)  and  10  c.c.  of  95  per  cent  alcohol.  Connect 
the  flask  with  a  return-flow  condenser  and  heat  on  a  water- 
bath  so  that  the  alcohol  boils  vigorously  for  25  minutes.  At 
the  end  of  this  time,  disconnect  the  flask  and  evaporate  off  the 
alcohol  on  a  boiling  water-bath.  After  the  complete  removal  of 
the  alcohol,  add  140  c.c.  of  recently  boiled  distilled  water  which 
has  been  cooled  to  about  50  degrees.  The  water  should  be  added 
slowly,  a  few  cubic  centimeters  at  a  time.  W'arm  the  flask  on 
the  water-bath  until  a  clear  solution  of  the  soap  is  obtained. 
Cool  the  solution  to  about  60  degrees  and  add  8  c.c.  of  sulphuric 
acid  (i  :  4)  to  set  free  the  fatty  acids.  Drop  two  bits  of  pumice, 
about  the  size  of  a  pea,  into  the  flask,  close  it  by  a  well-fitting 
cork,  which  is  tied  in  with  twine,  and  immerse  it  in  boiling 
water  until  the  fatty  acids  have  melted  to  an  oily  layer  floating  on 
the  top  of  the  liquid.     Cool  the  flask  to  about  60  degrees,  re- 


l68  AIR,  WATER,  AND   FOOD 

move    the   cork,    and    immediately    attach    the    flask   to    the 
condenser. 

Distill  no  c.c.  into  a  graduated  flask  in  as  nearly  thirty  min- 
utes as  possible.  Thoroughly  mix  the  distillate,  pour  the  whole 
of  it  through  a  dry  filter,  and  titrate  loo  c.c.  of  the  mixed  filtrate 

N  .  .  ... 

with  —  sodium  hydroxide,  using  phenolphthalem  as  an  mdicator. 

lO 

Multiply  the  number  of  cubic  centimeters  of  alkali  used  by 

eleven-tenths,  and  correct  the  reading  also  for  any  weight  of 

fat  greater  or  less  than  5  grams. 

For  example,  if  5.3  grams  of  butter-fat  are  used,  and  100  c.c. 

N 
of  the  distillate  require  27.4  c.c.  of  —  NaOH,  no  c.c.  would  re- 

10 

quire    27.4  X  y^  =  30.14    c.c.     Then    5.3  :  30.14  =  $  :  x.  x  = 

28.4.     X  is  the  Reichert-Meissl  number. 

Notes.  —  The  Reichert-Meissl  number  for  genuine  butter 
varies  from  24  to  34;   the  average  usually  taken  is  28.8. 

Cocoanut  oil  gives  a  value  of  6-8;  other  edible  fats  and  oils 
have  a  value  usually  less  than  i . 

Cocoanut  oil  is  used,  to  some  extent,  as  a  substitute  for  butter 
in  confections  and  crackers,  in  cooking  fats,  and  also  in  cocoa- 
butter  substitutes.  Its  presence  is  indicated  by  the  Reichert- 
Meissl  number  taken  in  connection  with  the  saponification  value, 
that  is,  the  number  of  milligrams  of  potassium  hydroxide  re- 
quired to  saponify  one  gram  of  the  fat.  (For  a  description  of 
the  method  of  determining  this  see  Lewkowitsch:  Oils,  Fats 
and  Waxes;  or  Gill:  A  Short  Handbook  of  Oil  Analysis.)  The 
Reichert-Meissl  number  is  higher  in  butter  fat  than  in  cocoanut 
oil,  while  the  saponification  value  is  lower.  In  pure  butter  fat 
the  value  of  the  expression: 

Saponification  value  —  (Reichert-Meissl  number  —  200)  varies 
from  3.4  to  4.1;  in  pure  cocoanut  oil,  it  runs  from  47  to  50.7.* 

Another  method  of  value  in  showing  the  presence  of  cocoanut 
oil  is  the  determination  of  the  Polenske  numberf  which  repre- 

*  Juckenack  and  Pastcrnack:  Ztschr.  Nahr.  Gemissm.,  7,  1904,  193. 
t    Polenske:  Zlschr,  Nahr.  Gcnussm.,  1904,  273. 


ANALYTICAL  METHODS  1 69 

sents  the  volatile  fatty  acids  insoluble  in  water.  This  value  for 
butter  is  from  i  to  3;  for  cocoanut  oil,  from  16  to  18.  Details 
of  the  procedure,  which  it  requires  some  experience  to  carry  out 
successfully,  may  be  found  in  the  original  paper  or  in  Leach's 
Food  Analysis,  3d  ed.,  page  483. 

The  reactions  involved  in  the  Reichert-Meissl  method  may  be 
simply  explained  as  follows: 

When  the  fat  is  treated  with  potash  it  is  decomposed,  the 
glycerine  being  set  free,  and  the  potassium  salts  of  the  fatty 
acids,  that  is  to  say,  the  potassium  soaps,  are  formed.  Hence 
the  process  is  called  saponification.  For  butyric  acid  the  re- 
action may  be  expressed, 

C3H5(C3H7COO)3  +  3  KOH  =  3  C3H7COOK  +  C3H5(OH)3. 

The  alcohol  is  used  to  dissolve  the  fat.  But  at  the  moment 
the  butyric  acid  is  set  free  it  tends  to  combine  with  the  alcohol  to 
form  a  volatile  ether: 

C3H7COOH  +  C2H5OH  =  C3H7COOC0H5  +  HoO. 

The  object  of  the  return-flow  condenser  is  to  prevent  the  escape 
of  this  volatile  ether  and  to  allow  of  its  complete  saponification. 

If  the  water  used  to  dissolve  the  soap  is  added  too  rapidly, 
the  soap  may  be  decomposed  with  the  liberation  of  the  fatty 
acids:  C3H7COOK  +  H.2O  =  C3H7COOH  +  KOH. 

The  fatty  acids  are  set  free  at  the  proper  time  by  means  of 
sulphuric  acid,  and  the  volatile  acids  distilled  off  and  titrated. 
The  pumice  is  added  to  prevent  explosive  boiUng. 

The  whole  of  the  volatile  acids  do  not  pass  over  into  the  dis- 
tillate, but  only  a  part,  the  amount  depending  upon  the  rate  of 
distillation  and  the  volume  of  the  distillate.  Hence,  in  order  to 
get  uniform  results,  it  is  necessary  to  follow  the  prescribed  pro- 
cedure with  great  care. 

In  Great  Britain  all  determinations  of  the  Reichert-lNIeissI 
number,  which  are  likely  to  lead  to  prosecutions  under  the  ]\Iar- 
garine  Act,  must  be  made  in  a  specified  apparatus,  the  dmiensions 
of  which  are  definitely  stated  and  the  procedure  exactly  defined.* 

*  Analyst,  25,  1900,  309. 


lyo  AIR,  WATER,  AND   FOOD 

Some  of  the  errors  in  the  Reichert-Meissl  method  may  be 
avoided,  and  the  process  materially  shortened  by  carrying  out 
the  saponification  with  glycerol  and  caustic  soda  as  recommended 
by  Leffman  and  Beam.*     The  method  is  as  follows: 

Weigh  5  grams  of  the  fat  into  a  250-c.c.  round-bottomed 
flask  and  add  20  c.c.  of  glycerol-soda  solution. f  Hold  the  flask 
with  tongs,  and  heat  it  directly  over  a  flame  until  foaming  ceases 
and  the  mixture  becomes  perfectly  clear,  which  ordinarily  re- 
quires about  five  minutes.  Add  to  the  clear  soap  solution  135 
c.c.  of  water,  adding  it  at  first  in  very  small  portions  to  prevent 
foaming.  Finally  add  the  pumice  and  sulphuric  acid,  as  in  the 
Reichert-Meissl  method,  and  distill  without  previous  melting  of 
the  fatty  acids. 

(2)  Hehner's  Method  for  Direct  Determination  of  the  Fixed 
Fatty  Acids.  —  Directions.  —  To  the  portion  of  2.5  grams 
weighed  out  into  the  500-c.c.  beaker  add  i  c.c.  of  caustic  potash 
and  20  c.c.  of  95  per  cent  alcohol.  Cover  the  beaker  with  a 
watch-glass  and  heat  it  on  the  water-bath  until  the  liquid  is 
clear  and  homogeneous.  As  it  is  not  essential  to  prevent  the 
escape  of  the  volatile  acids,  the  use  of  a  return-flow  condenser 
is  not  necessary.  Evaporate  off  the  alcohol  on  the  water-bath 
and  dissolve  the  soap  in  about  400  c.c.  of  warm  distilled  water. 
When  the  soap  is  completely  dissolved,  add  10  c.c.  of  hydro- 
chloric acid  (sp.  gr.  1.12),  and  heat  the  beaker  in  the  water- 
bath  almost  to  boiling  until  the  clear  oil  floats.  Meanwhile,  dry 
and  weigh  a  thick  filter  in  a  small  covered  beaker.  Allow  the 
solution  to  cool  until  the  fat  forms  a  sohd  cake  on  top;  filter  the 
clear  liquid  and  finally  bring  the  solid  fats  upon  the  weighed 
filter.  Wash  the  beaker  and  fat  thoroughly  with  cold  water, 
then  wash  out  the  fat  adhering  to  the  beaker  with  boiling  water, 
which  is  poured  through  the  filter,  taking  care  that  the  filter  is 
never  more  than  two-thirds  full.  If  the  filter  paper  is  of  good 
texture  and  thoroughly  wet  beforehand,  it  will  retain  the  fatty 
acids  completely.     If,  however,  oily  particles  are  noticed  in  the 

*  Analyst,  i8gi,  153. 

t  20  c.c.  of  50  per  cent  caustic  soda  solution  to  180  c.c.  of  glycerol. 


ANALYTICAL   METHODS  171 

filtrate,  cool  it  by  adding  pieces  of  ice,  remove  the  solidified  par- 
ticles with  a  glass  rod  and  transfer  them  to  the  filter.  Cool  the 
funnel  by  plunging  it  into  cold  water,  remove  the  filter,  place  it 
in  the  weighing-beaker,  and  dry  it  at  100°  to  constant  weight. 
The  fat  should  be  heated  about  an  hour  at  first,  then  for  periods 
of  about  thirty  minutes,  until  the  weight  is  constant  within 
2  mgs. 

Notes.  —  87.5  per  cent  is  usually  taken  as  the  proportion  of 
fixed  fatty  acids  in  butter-fat;  88  and  89  per  cent  have  been 
frequently  found.  All  other  fats  yield  from  95  to  96  per  cent 
of  insoluble  fatty  acids. 

(3)  Determination  of  Iodine  Value.  —  This  method  is  based 
on  the  fact  that  certain  of  the  fatty  acids,  notably  the  "unsatu- 
rated acids,"  as  oleic  acid,  C17H33COOH,  take  up  the  halogens 
with  the  formation  of  addition  products. 

Directions.  —  Dissolve  the  fat  in  the  300-c.c.  bottles  in  10  c.c. 

of  chloroform.     Add  30  c.c.  of  the  iodine  solution  from  a  pipette 

or  glass-stoppered  burette,  and  allow  the  bottles  to  stand  with 

occasional  shaking  for  thirty  minutes.     Add  10  c.c.  of  20  per 

cent  potassium  iodide  solution  and  mix  thoroughly,  then  100  c.c. 

.     .        .     N 
of  distilled  water,  and  titrate  the  excess  of  lodme  with  —  sodium 

10 

thiosulphate  until  the  solution  is  faintly  yellow.  Add  2  to  3  c.c. 
of  starch  solution  and  titrate  to  the  disappearance  of  the  blue 
color.  Toward  the  end  of  the  titration  shake  the  bottle  vigor- 
ously so  that  any  iodine  remaining  in  the  chloroform  may  react 
with  the  thiosulphate.  Calculate  the  result  in  grams  of  iodine 
absorbed  by  100  grams  of  fat.  This  is  called  the  Iodine 
Number,  or  Iodine  Value. 

At  the  time  of  making  the  determination  carry  out  two 
"blanks"  in  exactly  the  same  way  except  that  no  fat  is  used. 

Standardization  of  the  Thiosulpliate  Solution.  — As  this  is  not 
pennanent,  its  strength  should  be  determined  by  means  of  the 
standard  potassium  bichromate  solution,  i  c.c.  of  which  is 
equivalent  to  0.0 1  gram  of  iodine. 

Measure  20  c.c.  of  the  potassium  bichromate  from  a  pipette 


172  AIR,   WATER,   AND   FOOD 

into  an  Erlenmeyer  flask.  Add  5  c.c.  of  potassium  iodide,  100 
c.c.  of  water,  and  5  c.c.  of  strong  hydrochloric  acid.  Titrate  the 
liberated  iodine  with  the  thiosulphate  solution  until  the  color 
has  almost  disappeared,  then  add  starch  solution  and  continue 
the  titration  until  the  blue  color  disappears,  leaving  the  sea- 
green  color  of  the  chromium  chloride.  The  iodine  is  Hberated  in 
accordance  with  the  following  equation: 
KsCr.Oy  +  14  HCl  +  6  KI  =  8  KCl  +  2  CrCls  +  7  H2O  +  6  I. 

Calculation  of  Results.  —  Example.  —  From  the  standardi- 
zation, 

16.07  c-c.  thiosulphate  =  20  c.c.  bichromate  =  0.200  gram  I; 
I  c.c.  thiosulphate  =  0.0125  gram  I. 

Also,  from  blank, 

30  c.c.  iodine  solution  =  63.60  c.c.  thiosulphate. 

If  44.85  c.c.  thiosulphate  were  used  to  titrate  the  excess  of 
free  iodine,  63.60  —  44.85  =  18.75  c.c.  is  the  amount  of  thio- 
sulphate equivalent  to  the  iodine  combined  with  the  fat.  If 
0.3271  gram  of  fat  were  used,  since  i  c.c.  thiosulphate  is  equiva- 

1     .  .  r       •  J-        18.75  X  0.0125  ^^  , . 

lent  to  0.0121:  gram  free  lodme,  — — X  100  =  71.66 

0.3271 

grams  of  iodine  combined  with  100  grams  fat. 

Notes.  —  The  Iodine  Number  of  butter  fat  varies  between  26 
and  38;  of  oleomargarine,  between  60  and  75;  of  lard,  between 
46  and  70;  of  cottonseed  oil,  from  106  to  no;  and  of  cocoanut 
oil,  between  8  and  9.5. 

The  products  formed  by  the  action  of  iodine  on  the  fats  are 
mainly  addition  products  with  a  slight  proportion  of  substituted 
bodies.     Thus  the  unsaturated  olein, 

(CnH33COO)3C3H5, 

takes  up  six  atoms  of  iodine,  forming  an  addition  product, 
di-iodo-stearin,  (Ci7H33l2COO)3C3H5. 

The  method  in  general  use  for  determining  the  iodine  value 
of  fats  and  oils  has  been  that  of  Baron  Hiibl,*  an  alcoholic  solu- 

*  Ding.  Poly.  J.,  253,  281;  /.  Soc.  Chem.  Ind.,  3,  1884,  641. 


ANALYTICAL   METHODS  1 73 

tion  of  iodine  and  mercuric  chloride  being  used  as  the  reagent. 
The  method  here  described,  due  to  Hanus,*  has  the  advantage 
that  the  solutions  keep  better,  remaining  practically  unchanged 
for  several  months,  and  that  the  action  is  about  sixteen  times 
as  rapid.  For  the  fats  and  for  oils  with  low  iodine  values,  the 
results  are  very  close  to  the  figures  obtained  by  the  Hiibl  proc- 
ess. If  it  is  desired  to  carry  out  the  determination  by  the 
older  method,  directions  can  be  found  in  any  standard  work  on 
the  analysis  of  oils. 

It  should  be  noted  that  the  "iodine  solution"  is  a  solution  of 
iodine  bromide  in  glacial  acetic  acid,  hence  great  care  should  be 
taken  that  there  is  no  change  in  temperature  between  the  time 
of  measuring  the  solution  of  iodine  for  the  blanks  and  for  the  de- 
terminations, since  the  high  coefficient  of  expansion  of  acetic 
acid  may  cause  a  material  error. 

Further,  the  amount  of  fat  taken  for  the  analysis  should  be 
such  that  only  a  portion  of  the  iodine  is  absorbed,  60  to  70  per 
cent  being  in  excess.  Care  should  also  be  taken  to  avoid  vigor- 
ous shaking  of  the  glass-stoppered  bottles  until  near  the  end  of 
the  titration  to  prevent  loss  of  iodine  from  the  stopper. 

(4)  Refractive  Index.  —  The  determination  of  the  refractive 
index  is  especially  valuable  in  the  examination  of  butter,  and  for 
that  matter,  in  food  analysis  in  general,  owing  to  the  rapidity 
with  which  the  test  can  be  made  and  the  fact  that  so  Httle  of  the 
substance  is  required.  Various  forms  of  refractometers  are 
used  for  the  purpose,  a  fairly  complete  description  of  which 
will  be  found  in  some  of  the  larger  works,  such  as  Leach:  Food 
Inspection  and  Analysis;  or  Vaubel:  Quantitative  Bestimmung 
organischer  Verbindungen.  The  instrument  having  the  widest 
range  is  the  Abbe  refractometer,  in  which  the  index  of  re- 
fraction is  determined  by  measuring  the  total  reflection  pro- 
duced by  a  very  thin  layer  of  the  melted  fat,  placed  between  two 
prisms  of  flint  glass.  This  instrument,  fltted  with  watcr-jackctcd 
prisms,  is  shown  in  Fig.  13. 

Directions.  —  Revolve  the  whole  instrument  on  the  axis  h  until 
*  Ztschr.  Unlcrs.  Nahr.  it.  Goiussm.,  4,  igoi,  913. 


174 


AIR,   WATER,   AND   FOOD 


it  reaches  the  stop  provided,  then  open  the  prism  casing  AB  hy 
giving  the  pin  v  a  half-turn  (to  the  right).  Be  sure  that  the 
prism  surfaces  are  clean.  If  not,  clean  them  carefully  with  a  soft 
cloth  and  a  little  alcohol.     Place  a  few  drops  of  the  melted 


Fig. 


13- 


sample  directly  on  the  surface  of  the  prism  and  clamp  the  two 
together  again  by  turning  the  pin  v  in  the  opposite  direction. 
Now  turn  the  instrument  back  (toward  the  observer)  as  far  as 
possible  and  bring  the  "critical  line"  into  the  field  of  vision  of 
the  telescope.  This  is  done  by  holding  the  sector  S  firmly  with 
the  hand  and  revolving  the  double  prism  by  means  of  the  alidade 
/  until  the  field  is  divided  into  a  light  and  a  dark  portion.     If 


ANALYTICAL  METHODS 


175 


the  line  is  not  sharp  focus  the  ocular  of  the  telescope.  If  it  is 
colored  it  is  due  to  dispersion  of  the  light  by  the  liquid  and 
should  be  corrected  by  revolving  the  compensator  T  by  the 
milled  screw  M.  The  correction  is  made  by  a  system  of  two  re- 
volving Amici  prisms  in  the  lower  part  of  the  telescope.  Adjust 
the  critical  line  so  that  it  falls  on  the  intersection  of  the  cross 
hairs  of  the  telescope.  Observe  the  temperature  by  the  ther- 
mometer inserted  in 
the  prism  casing.  In 
the  case  of  solid  fats, 
a  sufficiently  high 
temperature  should 
be  maintained  by  a 
current  of  warm 
water  to  keep  the 
sample  well  above  its 
melting  point.  A 
temperature  of  30  to 
40°  C.  is  usually  suffi- 
cient. Do  not  let  the  temperature  rise  above  70°  or  the  prisms 
may  be  injured.  Read  the  index  of  refraction  directly  through 
the  small  lens  L,  estimating  the  fourth  decimal.  Calculate  the 
value  for  the  refractive  index  at  25°  C. 

Notes.  —  The  principle  on  which  the  Abbe  refractometer  is 
based  will,  perhaps,  be  more  clearly  understood  by  reference  to 
Fig.  14. 

Let  AB  ht  the  surface  of  separation  between  two  media,  of 
which  the  upper  is  the  rarer,  and  let  a  beam  of  light  pass  through 
in  the  direction  10.  It  will  be  seen  that  as  the  light  passes  from 
the  denser  to  the  rarer  medium,  the  angle  of  refraction  r  will  be 
greater  than  the  angle  of  incidence  i.  If  the  angle  of  incidence 
be  increased,  then  for  a  certain  incident  angle,  the  angle  of  re- 
fraction will  become  90°,  that  is,  the  refracted  ray  will  coincide 
with  the  dividing  surface.  For  incident  rays  striking  the  sur- 
face at  a  greater  angle  than  this,  the  light  will  be  totally  reflected 
and  there  will  be  no  refracted  ray.     The  angle  of  incidence  at 


Fig. 


14. 


176 


AIR,   WATER,  AND   FOOD 


which  this  occurs  is  known  as  the  critical  angle. 

.  sin  i 

Then  since  n  =  —. — , 
stn  r 

...         ,  sin  i         sin  i         .     . 

at  the  critical  angle  n  =  —. x  =  =  sm  i. 

sm  90  I 

That  is,  in  passing  from  a  denser  to  a  rarer  medium,  the  index  of 
refraction  is  equal  to  the  sine  of  the  angle  of  incidence  for  the 
border  line  of  total  re- 
flection. '  ^^       ^      ^ 

In  the  Abbe  rcfrac- 
tometer  the  refractive 
index  of  the  liquid  is 
determined  by  measur- 
ing the  critical  angle 
for  light  passing   into 
it  from  a  glass  prism  of 
higher  refractive  index.     The  sine  of 
this  angle  is  the  index  of  refraction 
of  the  liquid,  referred  to  glass,  and 
this  multiplied  by  the  refractive  in- 
dex of  the  glass  gives  the  index  of 
refraction  of  the  liquid  referred  to  air. 
The  divisions  on  the  scale  are  pro- 
portional to  the  sines  of  the  angles 
of  incidence  for  total  reflection,  multi- 
plied by  1.75,  the  refractive  index  of 
the  prism  and,  therefore,  give  directly 
the  refractive  index  of  the  substance 
examined.     Since  the  light  must  pass 
from  the  denser  to  the  rarer  medium, 
it  is  evident  that  the  instrument  is 
limited  to  liquids  whose  refractive  indices  are  less  than  1.75. 

Fig.  15,  from  Browne's  Handbook  of  Sugar  Analysis,  illus- 
trates diagrammatically  the  passage  of  light  through  the  in- 
strument. The  heavy  line  represents  the  border  line  of  total 
reflection,  the  light  striking  the  surface  AB  at  a.  less  angle  being 


Fig.  15. 


ANALYTICAL  METHODS 


177 


refracted,  and  illuminating  the  field  of  the  telescope.  The  rays 
which  fall  upon  the  surface  at  a  greater  angle  are  totally  reflected, 
leaving  the  corresponding  portion  of  the  telescopic  field  dark. 

The  index  of  refraction  decreases  with  rising  temperature. 
With  the  common  oils  and  fats,  the  change  for  each  degree  is 
very  nearly  a  constant,  amounting  to  0.000365.  Leach  and 
Lythgoe  *  have  devised  a  sliding  scale  by  means  of  which  the 
temperature  correction  may  be  readily  made  without  reference  to 
tables. 

The  values  of  «|^  for  genuine  butter  lie  between  1.4590  and 
1.4620;  for  oleomargarine  the  values  range  from  1.4650  to 
1.4700. 

The  correctness  of  the  instrument  should  be  tested  by  the 
"test-plate"  which  comes  with  it,  cementing  it  to  the  prism 
with  monobromnaphthalene,  or  the  testing  may  be  done  more 
conveniently  with  distilled  water.  The  refractive  index  of  wat6r 
at  ordinary  temperatures  is  given  below: 


Tempera- 

Refractive 

Tempera- 

Refractive 

ture,  °C. 

Index. 

ture,  °C. 

Index. 

18 

^■3332 

23 

13327 

19 

I-333I 

24 

1.3326 

20 

1-3330 

25 

1-3325 

21 

I   3329 

26 

1-3324 

22 

1.3328 

27 

1-3323 

Special  Tests  for  Distinguishing  Renovated  Butter.  —  Spoon 
Test  or  "Foam''  Test.  —  Melt  a  piece  of  the  sample  as  large  as  a 
small  chestnut  in  an  ordinary  tablespoon  or  a  small  tin  dish. 
Use  a  small  flame  and  stir  the  melting  fat  with  a  splinter  of  wood 
(such  as  a  match).  Then  increase  the  heat  so  that  the  fat  shall 
boil  briskly,  and  stir  thoroug/dy,  not  neglecting  the  outer  edges, 
several  times  during  the  boiling. 

Oleomargarine  and  renovated  butter  boil  noisily,  usually 
sputtering  like  a  mixture  of  grease  and  water  when  boiled,  and 

*  J.  Am.  Chem.  Soc,  1904,  1193. 


178  AIR,  WATER,  AND   FOOD 

produce  little  or  no  foam.  Genuine  butter  usually  boils  with 
much  less  noise  and  produces  an  abundance  of  foam,  often  rising 
over  the  sides  of  the  dish  or  spoon  when  the  latter  is  removed 
temporarily  from  the  flame.  The  difference  in  regard  to  the 
foam  is  very  marked. 

Note  also  the  appearance  of  the  particles  of  curd  after  the 
boiling.  With  genuine  butter  these  will  be  very  small  and 
finely  divided,  hardly  noticeable  in  fact,  while  with  oleomargarine 
and  renovated  butter  the  curd  gathers  in  much  larger  masses 
or  lumps. 

Notes.  —  This  simple  method  is  of  value  for  giving  a  quick 
decision  regarding  a  sample,  and  is  especially  useful  for  the 
detection  of  renovated  butter.  The  dififerences  in  the  compo- 
sition of  butter-fat  brought  about  by  renovation  are  so  slight 
that  chemical  methods  are  here  of  no  avail. 

The  spoon  test,  however,  will  distinguish  in  the  great  majority 
of  cases  between  genuine  butter  on  the  one  hand  and  oleo- 
margarine and  renovated  butter  on  the  other;  the  index  of 
refraction  or  the  chemical  methods  just  described  readily  dis- 
tinguish between  the  two  latter. 

In  genuine  butter  the  curd  is  somewhat  different  in  compo- 
sition from  that  of  renovated  butter  or  oleomargarine  in  that  it 
consists  largely  of  the  milk  proteins  that  are  insoluble  in  water, 
and  hence  accompany  the  separated  cream.  The  curd  of  reno- 
vated butter  or  oleomargarine,  on  the  other  hand,  comes  from 
the  proteins  of  the  milk  added  directly  in  the  process  of  manu- 
facture, and  consists  mainly  of  coagulated  casein.  Hence  its 
different  appearance  in  the  test. 

The  crackhng  and  sputtering  of  the  fat  in  the  case  of  oleo- 
margarine and  renovated  butter  are  due  to  the  fact  that  in  the 
process  of  manufacture  of  these  the  melted  fat  is  sprayed  into 
ice-water,  and  the  cooled  particles  enclose  some  water. 

Microscopic  Examination.  —  Pure,  fresh  butter  is  not  ordi- 
narily crystalHne  in  structure.  Butter  which  has  been  melted, 
however,  and  fats  which  have  been  liquefied  and  allowed  to  cool 
slowly  show  a  distinct  crystalline  structure,  especially  by  polar- 


ANALYTICAL  METHODS  179 

ized  light.  If  only  fresh  butter  were  sold,  and  all  adulterants 
had  been  previously  melted  and  slowly  cooled,  this  method  would 
be  all  that  would  be  necessary  for  the  detection  of  adulteration. 
As  it  is,  however,  it  is  most  useful  in  making  comparative  exami- 
nations of  samples  which  have  been  subjected  to  the  same 
conditions. 

About  the  most  that  can  be  said  is  that  if  a  small  bit,  about 
the  size  of  a  pin-head,  of  the  fresh,  unmelted  sample,  is  taken 
from  the  center  of  the  mass  and  pressed  out  on  a  sUde  by  gentle 
pressure  on  the  cover  glass,  it  ought  to  show  a  fairly  uniform 
field  if  examined  with  a  one-sixth  objective,  using  polarized 
light  and  a  selenite  plate.  Other  fats  melted  and  cooled,  and 
mixed  with  butter,  generally  show  a  crystalline  structure  and  a 
variegated  color  with  the  selenite  plate. 

In  the  case  of  renovated  butter,  however,  there  is  a  distinct 
difference  to  be  noted  in  the  appearance  of  the  field.  With 
genuine  butter  the  field  is  much  more  clear  and  free  from  opaque 
masses  of  curd  than  with  renovated  butter.  When  the  slide  is 
examined  by  reflected  light,  turning  the  mirror  so  as  not  to  pass 
light  through  the  slide,  these  opaque  masses  in  the  case  of  reno- 
vated butter  show  strikingly  as  white  masses  against  a  dark 
background. 

CEREALS 

The  great  importance  of  cereal  food  in  the  diet  may  be 
gathered  from  the  fact  that  dietary  studies  among  a  large  num- 
ber of  American  families  have  shown  that  about  three-fourths 
of  the  vegetable  protein,  one-half  of  the  carbohydrates,  and 
seven-eighths  of  the  vegetable  fat  are  supplied  by  the  cereals. 
The  reason  for  such  an  extensive  use  of  the  cereals  lies  in  the 
fact  that,  besides  being  cheap  and  easily  grown,  they  contain 
unusually  large  proportions  of  nutriment  with  a  very  small  pro- 
portion of  refuse.  They  are  readily  prepared  for  the  table,  are 
palatable  and  digestible.  In  distinction  from  the  two  classes  of 
food  materials  already  considered,  they  are  in  a  dry  fomi,  and 
not  liable  to  rapid  change  by  micro-organisms. 


l8o  AIR,   WATER,  AND   FOOD 

Prepared  breakfast  foods  may  be  taken  as  typical  and  inter- 
esting cereal  products,  and  since  many  of  these  are  somewhat 
modified  from  their  original  composition  by  cooking  or  by 
treatment  with  malt,  the  form  in  which  the  carbohydrates  are 
present  is  of  almost  equal  importance  with  the  determination  of 
nitrogen. 

The  fact  that  in  the  breakfast  cereals  the  process  of  manu- 
facture has  in  no  way  increased  their  actual  food  value  over  the 
grains  from  which  they  were  prepared,  as  pointed  out  in  Chapter 
VIII,  is  emphasized  by  the  figures  in  the  accompanying  table  in 
which  some  of  the  most  widely-used  preparations  are  compared 
with  the  original  grains.  It  will  be  observed  that  practically  the 
only  change  is  in  the  solubility  of  the  carbohydrates,  the  starch 
being  changed  in  part  to  dextrin.  In  the  case  of  the  malted  food, 
the  change  may  go  even  farther,  and  a  greater  or  less  amount  of 
reducing  sugar,  principally  maltose,  be  formed. 

Moisture.  —  Directions.  —  Spread  about  2  grams  of  the 
finely  ground  material  in  a  thin  layer  on  a  watch-glass  and  dry 
it  in  the  oven  at  100°  C.  for  five  hours.  On  account  of  the 
ready  absorption  of  moisture  by  the  dried  sample,  the  use  of 
clipped  watch-glasses  will  be  found  advantageous. 

Note.  —  With  some  substances  drying  in  a  current  of  hydro- 
gen or  some  inert  gas  may  be  necessary,  but  for  most  cereals  the 
method  given  will  be  found  satisfactory. 

Ash.  —  Directions.  —  Weigh  about  2  grams  into  a  platinum 
dish,  such  as  is  used  for  the  determination  of  solids  in  milk,  and 
char  it  carefully.  Ignite  at  a  very  low  red  heat  until  the  ash  is 
white,  preferably  in  a  mufSe. 

Notes.  —  If  a  white  ash  cannot  be  obtained  in  this  manner, 
exhaust  the  charred  mass  with  water,  collect  the  insoluble 
residue  on  a  filter,  burn  it,  add  this  ash  to  the  residue  from  the 
evaporation  of  the  aqueous  extract  and  heat  the  whole  at  a  low 
red  heat  until  the  ash  is  white. 

Some  cereals,  such  as  whole  wheat  and  barley,  will  act  de- 
structively on  platinum  dishes,  on  account  of  the  phosphates 
present,  but  can  be  ignited  safely  in  platinum  in  the  muffle. 


ANALYTICAL  METHODS 


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l82  AIR,   WATER,   AND   FOOD 

Fat:  Ether  Extract.  —  Dircclions.  —  Place  the  residue  from 
the  determination  of  moisture,  as  described  above,  in  a  porous 
paper  cup  and  extract  it  with  pure  anhydrous  ether  for  sixteen 
hours,  using  the  Soxhlet  extractor  and  electric  heater  as  de- 
scribed on  page  141.  Evaporate  off  the  ether  and  dry  the 
residual  fat  at  the  temperature  of  boiling  water  to  constant 
weight. 

Note.  —  The  ether  extract  of  cereals  is  not  pure  fat  but  may 
contain  more  or  less  coloring  matter  or  resins.  Petroleum  ether 
can  be  used  for  the  extraction,  giving  results  not  essentially 
different  from  those  obtained  with  anhydrous  ethyl  ether. 

Total  Protein:  Determination  of  Nitrogen  by  the  Kjeldahl 
Process.*  —  This  method  is  based  upon  the  decomposition  of 
the  nitrogenous  material  by  boiling  with  strong  sulphuric  acid. 
The  carbon  and  hydrogen  are  oxidized  to  carbon  dioxide  and 
water,  a  portion  of  the  sulphuric  acid  being  reduced  to  sulphur 
dioxide.  The  nitrogen  is  left  as  ammonium  sulphate  from 
which  the  ammonia  is  liberated  by  potash  or  soda  and  distilled 
into  a  known  excess  of  standard  acid.  The  time  of  digestion 
can  be  materially  shortened  by  the  use  of  substances  like  mer- 
cury or  potassium  sulphate  which  assist  the  oxidation  or  raise 
the  boihng-point  of  the  acid. 

Directions.  —  Transfer  about  0.5  gram  of  the  finely  divided 
substance  from  a  weighing-tube  to  a  pear-shaped  digestion  flask, 
add  10  c.c.  of  concentrated  sulphuric  acid  free  from  nitrogen, 
and  0.2  gram  (three  small  drops)  of  metallic  mercury.  Place  a 
small  funnel  in  the  neck  of  the  flask,  which  should  be  sup- 
ported in  an  inclined  position  on  wire  gauze  and  heated  with  a 
small  flame  until  frothing  has  ceased  and  the  liquid  boils  quietly. 
Then  increase  the  heat  and  boil  the  solution  for  at  least  an 
hour  after  it  becomes  colorless.  Allow  the  flask  to  cool  for  a 
minute  or  two,  and  add  a  few  crystals  of  potassium  permanganate 
until  the  liquid  has  acquired  a  slight  green  or  purple  color. 

N 
Measure  25  c.c.  of  —  acid  from  a  burette  into  a  300-c.c. 

*  Ztschr.  anal.  Client.,  22,  1SS3.  366. 


ANALYTICAL  METHODS  183 

Erlenmeyer    flask    and   place    the    condenser-tip    beneath    the 

surface  of  the  liquid,  adding  a  little  water,  if  necessary,  to  seal 

it. 

Transfer  the  digestate  with  several  small  portions  of  distilled 

water  to  the  distilling  flask  of  the  apparatus,  add  20  c.c.  of 

potassium  sulphide  solution,   and   connect  the  flask  with  the 

condenser.     Add  50  c.c.  of  caustic  potash  through  the  separa- 

tory  funnel,  and  distill  off  the  ammonia  by  steam.     When  200 

c.c.  have  distilled  over,  remove  the  collecting-flask,  after  rinsing 

off  the  condenser-tip  with  distilled  water,  and  titrate  the  excess 

N         .  .  . 

of   acid   with   —    sodium   hydroxide,    usmg   methyl   orange   or 
10 

cochineal  as  indicator.  If  using  new  reagents,  a  blank  deter- 
mination should  be  made  with  0.5  gram  of  cane-sugar  in  order 
to  reduce  any  nitrates  present  which  might  otherwise  escape 
detection. 

Notes.  —  The  temperature  during  the  digestion  must  be 
maintained  at  or  near  the  boiling-point  of  the  acid,  since  at  a 
lower  temperature  the  formation  of   ammonia  is  incomplete. 

In  some  cases,  the  potassium  permanganate  is  necessary  to 
insure  the  complete  conversion  of  the  nitrogenous  bodies  into 
ammonia,  although  it  is  probable  that  its  use  is  unnecessary  in 
the  majority  of  analyses. 

The  addition  of  potassium  sulphide  before  distilling  is  to  pre- 
cipitate the  mercury  and  thus  prevent  the  formation  of  non- 
volatile mercur-ammonium  compounds. 

The  Kjeldahl  process  in  the  form  outlined  above  is  not  ap- 
plicable to  the  determination  of  nitrogen  in  the  form  of  nitrates. 
In  order  to  render  it  of  more  general  application  various  modi- 
fications of  the  method  have  been  proposed,  the  one  generally 
used  in  this  country  being  that  suggested  by  Scovcll.*  In  this 
method  salicylic  acid  is  used  with  the  sulphuric  acid,  being  con- 
verted by  the  nitrate  into  nitro-phenol.  By  the  use  of  sodium 
thiosulphate  or  zinc-dust  this  is  reduced  to  amido-phenol.  The 
amido-phenol  is  transformed  into  ammonium  sulphate  by  the 
*  U.  S.  Dept.  Agr.,  Bull.  16,  1SS7,  51. 


l84  AIR,  WATER,   AND   FOOD 

heating  with  sulphuric  acid,  the  use  of  mercury  being  absolutely 
necessary  in  this  case  to  secure  the  complete  transformation.  It 
is  true  also  that  certain  other  nitrogenous  bodies,  notably  the 
alkaloids  and  certain  organic  bases,  do  not  yield  all  their  nitro- 
gen to  the  Kjeldahl  process  without  modifications  which  com- 
plicate the  method.  For  a  discussion  of  the  efi&ciency  of  these 
various  modifications  the  student  is  referred  to  a  paper  by 
Sherman  and  Falk.*  In  the  case  of  cereals,  however,  and  with 
the  majority  of  food  products,  the  simpler  method  outlined  will 
prove  entirely  satisfactory. 

The  per  cent  of  proteids  may  be  found  by  multiplying  the 
per  cent  of  nitrogen  by  an  appropriate  factor,  the  one  in  general 
use  being  6.25.  Recent  work  has  shown,  however,  that  most 
of  the  proteids  of  cereals  contain  more  than  16  per  cent  of 
nitrogen,  so  that  the  factor  6.25  gives  results  that  are  too  high. 
Because  all  the  older  work  was  calculated  on  this  factor,  it  is 
still  generally  used,  nevertheless. 

Kjeldahl-Gunning  Method.  —  The  Gunning  method  can  be 
used  in  all  cases  where  the  Kjeldahl-Wilfarth  modification,  just 
described,  is  employed,  and  in  some  ways  it  is  simpler. 

The  digestion  and  distillation  are  carried  out  as  described  on 
page  182,  using  the  same  amount  of  sample,  together  with  20  c.c. 
of  concentrated  sulphuric  acid  and  10  grams  of  powdered  potas- 
sium sulphate.  No  mercury  and,  consequently,  no  potassium 
sulphide  is  used.  100  c.c.  of  the  potash  should  be  added  in- 
stead of  50. 

Note.  —  The  potassium  sulphate  is  added  to  raise  the  boiling 
point  of  the  sulphuric  acid  and  thus  shorten  the  time  required 
for  the  digestion. 

Carbohydrates.  —  The  total  carbohydrates,  often  stated  in 
analyses  as  "nitrogen-free  extract,"  may  be  readily  obtained  by 
subtracting  from  100  the  sum  of  the  percentages  of  the  other 
constituents,  viz.,  moisture,  ash,  ether  extract,  and  nitrogenous 
bodies.  In  many  cases,  however,  especially  with  the  cooked  or 
treated  cereals  and  with  such  classes  of  cereal  preparations  as 

*  J.  Am.  Chem.  Soc,  1904,  1469. 


ANALYTICAL   METHODS  185 

infant  or  invalid  foods,  a  further  study  of  the  carbohydrates  is 
desirable.  These  are  made  up  of  two  general  classes:  (a)  soluble 
carbohydrates,  including  sugars,  as  sucrose,  dextrose  and  maltose, 
dextrin  and  soluble  starch,  by  the  latter  term  being  meant  starch 
which  is  soluble  in  water  but  still  gives  the  characteristic  blue 
color  with  iodine,  in  distinction  from  some  of  the  more  com- 
pletely broken-down  forms  like  dextrin,  which  no  longer  give 
blue  or  purple  colors  with  iodine;  (b)  insoluble  carbohydrates,  in- 
cluding starch,  pentosans,  lignin  bodies,  and  cellulose.  The 
three  latter  occur  chiefly  in  the  husk  or  envelope  of  the  grain 
or  in  the  woody  fiber  of  the  plant.  The  pentosans  or  gums  are 
distinguished  from  one  another  by  the  formation  of  specific 
sugars  upon  hydrolysis  with  acids.  For  ordinary  analytical 
purposes  it  is  sufficient  to  determine  the  lignin  and  cellulose  to- 
gether as  "crude  fiber."  Since  the  exact  procedure  to  be  fol- 
lowed in  the  determination  of  the  carbohydrates  varies  largely 
with  each  specific  case,  only  a  general  outhne  can  be  presented 
here. 

Sugars.  —  The  finely  ground  material,  previously  dried  and 
extracted  with  ether  for  the  removal  of  crude  fat,  is  extracted 
with  85  per  cent  alcohol.  In  the  extract  the  reducing  sugars 
may  be  determined  by  means  of  Fehling's  solution  as  described 
on  page  145,  and  the  sucrose  determined  in  the  same  way  after 
inversion  with  hydrochloric  acid. 

Dextrin  and  Soluble  Starch.  —  The  residue  from  the  extrac- 
tion of  the  sugars  is  treated  for  eighteen  to  twenty-four  hours 
with  water  at  laboratory  temperature  with  frequent  agitation, 
made  up  to  definite  volume,  and  filtered.  This  may  be  tested 
with  iodine,  and  if  no  blue  color  is  produced,  evaporated  to  small 
volume,  and  the  dextrin  converted  to  dextrose  by  dilute  hydro- 
chloric acid  and  determined  by  FehUng's  solution.  In  some  few 
cases,  however,  a  blue  color  with  iodine  may  indicate  the  presence 
of  soluble  starch,  in  which  case  an  aliquot  part  of  the  filtrate  may 
be  treated  with  an  excess  of  barium  hydroxide  to  precipitate 
the  starch.  In  the  filtrate  from  this  precipitate  the  dextrin  is 
determined  by  inversion  and  copper  reduction  as  before.     The 


l86  AIR,  WATER,  AND   FOOD 

difference  between  the  dextrin  thus  found  and  the  first  deter- 
mination gives  the  soluble  starch. 

Starch.  —  This  may  be  determined  in  the  residue  insoluble  in 
cold  water  by  digesting  it  with  malt  extract,  and  determining  the 
dextrose  after  hydrolysis  with  dilute  acid.  It  is  more  common, 
however,  to  determine  the  starch  and  other  insoluble  carbo- 
hydrates directly  on  the  original  material.  The  methods  for  the 
determination  of  starch  vary  with  the  condition  in  which  the 
starch  is  found.  In  the  case  of  nearly  pure  starch  it  may  be 
converted  into  dextrose  by  boiling  with  dilute  acid,  the  dextrose 
being  then  determined  by  Fehling's  solution  in  the  usual  way. 
Hot  acids,  however,  cannot  be  used  to  convert  starch  in  the 
natural  state,  as  it  is  found  in  cereals,  because  other  carbohydrate 
bodies,  especially  the  pentosans,  become  soluble  under  these 
conditions  and  the  results  are  too  high.  In  such  cases,  the 
starch  is  brought  into  solution  by  treatment  with  diastase  or  by 
heating  with  water  under  pressure.  The  results  obtained  by 
direct  acid  hydrolysis,  however,  in  cases  where  the  highest 
accuracy  is  not  required,  may  be  sufficient  and  the  method  is 
much  quicker  and  easier  of  execution  than  the  digestion  with 
diastase. 

Direct  Acid  Hydrolysis.  —  Directions.  —  Weigh  out  from  2  to 
5  grams  of  the  sample,  depending  upon  the  amount  of  starch 
present,  and  wash  on  a  filter  with  five  successive  portions  of 
10  c.c.  each  of  ether.  Allow  the  ether  to  evaporate  from  the 
residue  and  then  wash  it  with  10  per  cent  alcohol  until  free  from 
soluble  carbohydrates.  150  c.c.  of  the  dilute  alcohol  is  generally 
sufficient,  but  if  much  reducing  sugar  or  dextrin  is  present,  as 
may  be  the  case  with  malted  cereals,  more  will  be  necessary. 
Wash  the  residue  from  the  filter  with  200  c.c.  of  water  into  a 
500  c.c.  graduated  flask,  add  20  c.c.  of  hydrochloric  acid,  sp.  gr. 
1. 1 25,  place  a  funnel  in  the  neck  of  the  flask  to  retard  evapo- 
ration, and  heat  in  a  boiling  water-bath  for  two  and  one-half 
hours.  Cool,  nearly  neutralize  with  sodium  hydroxide  and 
make  up  to  500  c.c.  Filter,  and  determine  dextrose  in  an 
aliquot  portion,  25  or  50  c.c.  of  the  filtrate,  using  the  method  de- 


ANALYTICAL   Mf:THODS  187 

scribed  on  page  145.  Convert  dextrose  to  starch  by  the  factor 
0.9. 

Note.  —  The  washing  to  remove  soluble  carbohydrates  is  per- 
formed with  dilute  alcohol  rather  than  with  water,  because  the 
former  is  less  likely  to  carry  starch  granules  through  the  paper. 
The  sugar  solution  when  added  to  the  Fehling's  solution  should 
be  clear  and  only  faintly  acid.  It  should,  in  general,  contain 
not  more  than  0.5  per  cent  of  reducing  sugar. 

Determination  with  Diastase.  —  Directions.  —  Treat  2  to  5 
grams  of  the  sample  with  ether  and  dilute  alcohol,  as  in  the 
previous  method,  and  wash  the  residue  into  a  250-c.c.  flask 
with  50  c.c.  of  water.  Heat  slowly  to  boiling,  or  immerse  the 
flask  in  boiling  water,  until  the  starch  gelatinizes,  stirring  con- 
stantly to  prevent  the  formation  of  lumps.  Cool  to  55°  C,  add 
20  to  40  c.c.  of  malt  extract,  and  keep  the  solution  within  two 
degrees  of  the  stated  temperature  for  an  hour  or  until  the  solu- 
tion no  longer  gives  the  starch  reaction  with  iodine  under  the 
microscope.  In  either  case,  heat  the  solution  again  to  boiling 
to  gelatinize  any  remaining  starch  granules,  test  again  and  if 
starch  is  found,  cool  to  55°  C,  and  treat  as  before,  using  a 
fresh  portion  of  malt  extract.  Continue  this  treatment  until, 
when  carefully  examined  under  the  microscope,  a  drop  of  the 
solution  fails  to  give  the  iodine  reaction  for  starch.  Cool, 
make  up  to  250  c.c.  and  filter  through  a  dry  filter.  Transfer 
200  c.c.  of  the  filtrate  to  a  500-c.c.  graduated  flask,  add  20  c.c. 
of  hydrochloric  acid,  sp.  gr.  1.125,  and  carry  out  the  determina- 
tion as  described  in  the  preceding  method. 

A  blank  determination  must  be  carried  through,  using  50  c.c. 
of  water  and  exactly  the  same  amount  of  malt  extract  as  used  in 
the  regular  procedure,  in  ©rder  to  correct  for  the  cupric  reducing 
power  of  the  malt  extract. 

Malt  Extract.  —  Treat  40  grams  of  fresh  coarsely  ground  malt 
several  hours  with  200  c.c.  of  w^ater,  shaking  occasionally. 
Filter  and  add  a  few  drops  of  chloroform  to  prevent  the  growth 
of  molds. 

Notes.  —  The  action  of  the  diastase  on  the  gelatinized  starch 


l88  AIR,   WATER,   AND   FOOD 

is  to  convert  it  into  maltose  and  dextrin,  that  is,  into  soluble 
bodies  that  can  be  separated  by  filtration  from  the  pentosans 
and  other  carbohydrates  that  give  the  high  results  in  the  direct 
acid  method.  By  the  action  of  acid  (hydrolysis)  the  maltose  and 
dextrin  are  converted  to  dextrose. 

The  determination  should,  if  possible,  be  carried  through 
without  interruption.  In  case  this  cannot  be  done,  saHcylic  acid 
may  be  used  to  prevent  fermentation,  not  adding  it,  however, 
until  after  the  digestion  with  diastase. 

If  the  malt  itself  is  not  readily  procurable,  certain  forms  of 
prepared  diastase  are  on  the  market  and  may  be  found  more 
convenient  either  for  analytical  use  or  for  purposes  of  illustration. 
When  possible,  however,  it  is  preferable  to  use  the  freshly  pre- 
pared malt  extract,  as  the  prepared  diastase,  made  at  different 
times  and  from  separate  portions  of  malt,  may  show  great  differ- 
ences in  hydrolytic  power. 

It  is  sometimes  convenient  to  use  freshly  collected  saliva, 
this  being  free  from  carbohydrate.  In  this  case,  the  digestion 
should  be  carried  out  at  38°  C.  instead  of  55°  C. 

Crude  Fibre.  —  The  Weende  method,  the  one  adopted  by  the 
Association  of  Official  Agricultural  Chemists,  is  based  on  the 
assumption  that  the  starch  and  other  digestible  carbohydrates 
and  protein  will  be  removed  from  the  cereal  by  successive  di- 
gestion at  a  boiling  temperature  with  acid  and  alkali  of  a  definite 
strength.  The  complex  body  thus  obtained  is  not  a  definite 
chemical  compound,  but  may  be  considered  as  being  composed 
largely  of  cellulose. 

Use  2  grams  of  the  finely-ground  sample  and  wash  on  a  filter 
with  5  portions  of  10  c.c.  each  of  ether.  (The  residue  from  the 
determination  of  "ether  extract"  can  be  used  if  desired.) 

Transfer  the  washed  material  to  a  500-c.c.  Erlenmeyer  flask, 
add  200  c.c.  of  boihng  1.25  per  cent  sulphuric  acid,  place  a 
funnel  in  the  neck  of  the  flask  and  boil  gently  for  30  minutes. 
Filter  on  a  ribbed  filter  and  wash  with  several  portions  of  boiling 
water.  Transfer  the  precipitate  by  means  of  200  c.c.  of  boiling 
1.25  per  cent  sodium  hydroxide  in  a  small  wash-bottle  to  the 


ANALYTICAL  METHODS  1 89 

same  500-c.c.  Erlenmeyer  flask,  and  boil  again  gently  for  30 
minutes. 

Filter  on  ignited  asbestos  in  a  Gooch  crucible,  wash  with 
boiling  water  until  free  from  alkali,  then  with  10  c.c.  of  alcohol, 
and  finally  with  10  c.c.  of  ether.  Dry  at  the  temperature  of 
boiling  water  to  constant  weight.  Ignite  carefully  at  first,  then 
at  a  low  red  heat  until  the  organic  matter  is  destroyed.  Calcu- 
late the  loss  on  ignition  as  "crude  fibre." 

Note.  —  The  filtration  will  be  found  to  proceed  fairly  rapidly 
if  the  solution  is  filtered  hot  and  care  is  taken  to  keep  the  residue 
from  the  filter  as  long  as  possible. 

The  sulphuric  acid  and  sodium  hydroxide  should  be  carefully 
prepared  and  the  strength  determined  by  titration. 

Examination  of  Malted  Cereals.  —  The  relation  of  the  carbo- 
hydrates in  a  malted  cereal,  which  ordinarily  consist  of  maltose, 
dextrin  and  starch,  may  be  readily  learned  by  the  following 
simple  analytical  scheme,  due  to  Sherman.* 

Directions.  —  Mix  5  grams  of  the  ground  sample  with  125  c.c. 
of  cold  water  in  a  250-c.c.  graduated  flask  and  allow  it  to  stand 
at  room  temperature  for  an  hour,  shaking  frequently.  Make 
up  to  the  mark,  mix  and  filter  through  a  dry  filter.  Determine 
the  reducing  sugar  in  25  c.c.  of  the  filtrate  as  described  on  page 
145,  and  calculate  as  maltose  in  the  original  sample.  Measure 
50  c.c.  of  the  same  filtrate  into  a  loo-c.c.  flask,  add  5  c.c.  of 
hydrochloric  acid  (sp.  gr.  1.12),  and  hydrolyze  as  directed  on 
page  186.  Filter  and  determine  the  dextrose  in  the  filtrate  as 
on  page  145.  Subtract  the  amount  due  to  maltose  and  calculate 
the  remainder  to  dextrin  by  multiplying  by  0.9. 

Treat  another  portion  of  the  original  sample  as  described  un- 
der the  determination  of  starch  by  acid  hydrolysis,  page  186, 
without,  how^ever,  extracting  the  soluble  carbohydrates.  From 
the  dextrose  found  subtract  that  given  by  dextrin  and  maltose 
and  calculate  the  remainder  to  starch. 

Notes.  —  The  presence  of  undissolved  material  in  the  flask 
when  diluted  to  volume  renders  the  result  somewhat  inaccurate, 

*  Methods  of  Organic  Analj'sis,  2d  Ed.,  p.  341. 


I  go  AIR,  WATER,  AND   FOOD 

and  the  possible  presence  of  other  reducing  sugars  than  maltose 
introduces  error,  but  the  results  are  sufficiently  close  for  com- 
parative tests. 

Examination  of  Fermented  Liquors 

WINE 

General  Statements.  —  The  object  of  a  wine  analysis  is  ordi- 
narily to  determine  whether  or  not  a  wine  is  pure  and  un- 
adulterated, or  whether  it  has  been  properly  made.  Special 
works  furnish  sufficient  information  concerning  processes  of 
manufacture,  and  it  is  essential  to  know  here  only  the  general 
composition  of  the  grape- juice  or  "must"  and  how,  by  the 
natural  process  of  fermentation,  this  may  be  altered  in  the 
finished  product. 

The  "must"  contains  sugars  (mainly  dextrose);  dextrin; 
organic  acids  and  salts,  mainly  tartaric  and  malic  acids;  salts  of 
inorganic  acids,  chiefly  phosphates,  sulphates,  and  chlorides. 
Various  extractive  matters,  which  largely  affect  the  color  and  flavor 
of  the  wine,  together  with  a  little  tannin  and  albuminous  sub- 
stances, are  also  present.  The  wine  will  contain,  then,  besides 
water,  the  following:  Alcohol,  glycerine,  frequently  some  sugar 
that  has  escaped  fermentation,  ethers,  which  determine  largely 
the  "bouquet"  of  the  wine,  and  more  or  less  of  the  acids,  salts, 
coloring  and  extractive  matters  of  the  must,  together  with  vary- 
ing amounts  of  carbonic,  acetic,  and  succinic  acids. 

According  to  differences  in  their  composition,  wines  may  be 
divided  into  various  classes,  such  as  "dry"  wines,  which  contain 
very  little  sugar,  as  distinguished  from  the  sweet  wines,  in  which 
a  notable  quantity  of  sugar  has  escaped  fermentation,  or  to 
which  an  addition  of  sugar  has  been  made  subsequent  to  the 
main  fermentation.  Or  they  may  be  divided  according  to  the 
content  of  alcohol  into  natural  wines  and  those  fortified  by  ad- 
dition of  alcohol,  as  port,  sherry,  and  madeira. 

The  composition  of  the  wine  may  be  changed,  moreover,  by 
the  various  methods  which  are  used  for  its  "improvement," 


ANALYTICAL   METHODS  191 

such  as  fortification  already  mentioned,  plastering,  petioiization, 
etc.  Information  regarding  these  methods  will  be  found  in 
some  of  the  larger  works  mentioned  in  the  bibliography. 

Determinations  of  value  in  judging  the  purity  of  wine  are 
alcohol,  glycerine,  extract,  ash,  total  and  volatile  acids.  The 
actual  percentages  of  these  substances  are  not  of  so  great  value  as 
certain  relations  between  them,  such  as  the  ratio  of  ash  to  extract, 
extract  to  alcohol,  alcohol  to  glycerine,  alcohol  to  acids,  and 
volatile  to  total  acids.  Examination  for  preservatives  and  for- 
eign coloring  matters  should  also  be  made.  It  should,  perhaps,  be 
stated  that  the  analytical  procedure  given  here  is  to  furnish 
practice  in  the  examination  of  a  fermented  food  product,  and  is 
by  no  means  as  thorough  as  might  be  needed  to  judge  the  quaHty 
or  genuineness  of  a  wine. 

Specific  Gravity.  —  This  is  to  be  taken  by  means  of  the 
pyknometer  at  15^.5  C. 

Notes.  —  Where  the  specific  gravity  of  the  sample  is  known, 
the  various  portions  taken  for  analysis  can  be  more  conven- 
iently measured  than  weighed.  The  results  can  be  calculated 
to  per  cent  by  weight  by  dividing  the  results  expressed  as  grams 
per  100  c.c.  by  the  specific  gravity. 

Effervescing  wines  should,  before  analysis,  be  vigorously 
shaken  in  a  large  flask  to  hasten  the  escape  of  carbon  dioxide. 
The  liquid  may  then  be  poured  from  under  the  foam  into  an- 
other vessel. 

Alcohol.  —  Principle.  —  The  alcohol  is  obtained  freed  from 
everything  but  water,  and  its  amount  determined  by  ascertain- 
ing the  specitic  gravity  of  the  mkture,  and  taking  the  per  cent 
from  the  tables. 

Directions.  —  Measure  (or  weigh)  100  c.c.  of  the  wine  into  a 
500-c.c.  round-bottomed  flask.  Add  50  c.c.  of  water  and  if  the 
wine  is  very  acid  a  small  pinch  of  precipitated  calcium  carbon- 
ate. With  most  wines  this  addition  will  not  be  necessary. 
Distill  about  95  c.c.  into  a  loo-c.c.  graduated  flask.  Fill  to  the 
mark  with  distilled  water,  mix  thoroughly,  and  take  the  specific 
gravity  of  the  distillate  at  15.5°  C.  with  a  pyknometer.     The  per- 


192  AIR,   WATER,   AND   FOOD 

centage  of  absolute  alcohol  by  volume  corresponding  to  the 
observed  density  will  be  found  in  Table  X,  page  217. 

To  find  the  alcohol  by  weight  in  the  sample,  multiply  the  per 
cent  of  alcohol  by  "weight  in  the  distillate  as  taken  from  the  table, 
by  the  weight  of  the  distillate  and  divide  the  result  by  the 
weight  of  the  sample  used. 

Notes.  —  The  addition  of  calcium  carbonate  is  to  prevent  the 
distillation  of  acetic  acid.  A  certain  amount  of  volatile  ethers 
may  also  pass  over  into  the  distillate,  but  it  is  so  slight  that  its 
influence  may  be  neglected. 

Normal  wines  ordinarily  contain  between  4.5  and  12  per  cent  of 
alcohol  except  in  the  case  of  "fortified"  wines,  where  the  amount 
may  be  even  20  per  cent.  Fermentation  does  not  yield  more 
than  about  14  per  cent  of  alcohol. 

Extract.  —  The  method  to  be  employed  depends  on  the  pro- 
portion of  extract.  A  preliminary  calculation  should  be  made 
by  the  aid  of  the  formula 

X  =  1  -{-  d  —  d', 
where  x  is  the  specific  gravity  of  the  dealcoholized  wine,  d  the 
specific  gravity  of  the  wine,  and  d'  the  specific  gravity  of  the 
distillate  obtained  in  the  determination  of  alcohol.     The  value 
for  X  is  found  from  Table  XI,  page  220. 

Dry  Wines.  —  (Having  an  extract  content  of  less  than  3  per 
cent.)  Evaporate  50  c.c.  on  the  water-bath  to  a  sirupy  con- 
sistency in  a  flat-bottomed  platinum  dish.  Heat  the  residue  in 
the  oven  at  100°  C.  for  two  hours  and  a  half,  cool  in  a  desiccator 
and  weigh. 

Sweet  Wines.  —  When  the  extract  content  is  between  3  and 
6  per  cent  treat  25  c.c.  of  the  sample  as  described  under  dry 
wines.  When  the  amount  of  extract  exceeds  6  per  cent  it  is  best 
to  accept  the  result  found  from  the  table  and  not  to  determine 
it  gravimetrically. 

Notes.  —  The  gravimetric  determination  will  be  inaccurate 
with  wines  high  in  extract  on  account  of  the  serious  error  caused 
by  dr>ing  levulose  at  high  temperatures.  The  figures  in  the 
table  are  based  on  determinations  made  at  75°  C.  in  vacuo. 


ANALYTICAL  METHODS  1 93 

Wine  made  from  the  juice  of  ripe  grapes  rarely  contains  less 
than  1.5  per  cent  of  extract  in  the  case  of  white  wines  and  about 
2.0  per  cent  in  the  case  of  red  wines.  The  amount  of  extract 
decreases  of  course  with  age. 

Alcohol-extract  Ratio.  —  The  municipal  laboratory  of  Paris 
considers  a  wine  "fortified"  if  the  alcohol  exceeds  4.5  times  the 
extract  for  red  wines  and  6.5  for  white  wines.  The  extract  and 
alcohol  should  both  be  expressed  in  per  cent  by  weight.  The 
amount  of  added  alcohol  is  calculated  by  the  municipal  labora- 
tory by  subtracting  the  "natural"  alcohol  (extract  X  4.5  or  6.5) 
from  the  total  alcohol. 

Ash.  —  Ignite  the  residue  from  the  extract  determination  as 
described  on  page  180. 

Note.  —  The  amount  of  ash  in  a  natural  wine  averages  about 
10  per  cent  of  the  extract,  varying  ordinarily  between  0.14  per 
cent  and  0.35  per  cent. 

Glycerine.  —  The  determination  of  glycerine,  and  the  ratio 
of  glycerine  to  alcohol  is  of  much  value  in  judging  the  purity  of 
a  wine.  The  determination  of  the  glycerine,  however,  is  rather 
difficult  and  requires  some  little  experience  in  order  to  obtain 
good  results.  The  official  method  of  the  Association  of  Agri- 
cultural Chemists  will  be  found  in  Bur.  of  Chem.,  Bull.  107, 
(Rev.  Ed.),  p.  83.  A  more  accurate  modification,  however,  is 
that  of  Ross  {Bull.  132,  p.  85). 

Free  Acids:    Total  Acidity  Calculated  as  Tartaric  Acid. — 

Measure  25  c.c.  of  the  wine  into  a  small  beaker,  heat  just  below 

...  .     .  N 

the  boilmg  pomt  to  expel  carbon  dioxide,  and  titrate  with  — 

10 

sodium  hydroxide   and  phenolphthalein.     In   the   case   of  red 

wines  use  delicate  red  litmus  paper,  taking  the  end-point  when 

a  drop  of  the  liquid  placed  upon  the  paper  produces  a  blue  spot 

in  the  middle  of  the  portion  moistened.     Calculate  the  results  as 

N 
tartaric  acid.     One  c.c.  — ■  sodmm  hydroxide  =  0.007^  gram  of 

tartaric  acid. 


194  AIR,  WATER,  AND   FOOD 

Volatile  Acids  Calculated  as  Acetic  Acid.  —  Measure  50  c.c. 

of  wine  into  a  300-c.c.  flask  provided  with  a  cork  having  two 

perforations.     One  is  fitted  with  a  tube  6  mm.  in  diameter  and 

blown  out  to  a  bulb  40  mm.  in  diameter  a  short  distance  above 

the  cork;   this  tube  is  connected  with  a  condenser.     The  other 

perforation  carries  a  tube  reaching  nearly  to  the  bottom  of  the 

flask  and  drawn  out  to  a  small  aperture  at  its  lower  end ;  this  is 

connected  with  a  500-c.c.  flask  containing  water.     Heat  both 

flasks  to  boiling;  then  lower  the  flame  under  that  containing  the 

wine,  adjusting  the  flame  so  that  the  volume  of  liquid  remains 

constant,  and  continue  the  distillation  by  means  of  steam  until  200 

.      N        . 
c.c.  have  distilled.     Titrate  the  distillate  with  — -  sodium  hydrox- 

10 

ide,  using  phenolphthalein  as  an  indicator.     Calculate  the  results 

N 
as  acetic  acid.     One  c.c.  —  sodium  hydroxide  =  0.0060  gram 

10 

of  acetic  acid. 

Hortvet  *  has  described  a  compact  self-contained  apparatus 
for  determining  the  fixed  and  volatile  acids  in  which  the  wine  is 
surrounded  by  boihng  water  while  the  steam  is  being  passed 
through,  giving  excellent  results. 

Fixed  Acids  Calculated  as  Tartaric  Acid.  —  These  may  be 
found  by  calculating  the  volatile  acids  as  tartaric  and  sub- 
tracting the  result  from  the  total  tartaric  acid  found  by  direct 
titration. 

Note.  —  The  total  acids  in  a  wine  vary  usually  between  0.45 
per  cent  and  1.5  per  cent.  The  acid  content  is  frequently 
diminished  by  aging  or  by  the  separation  of  cream  of  tartar. 
The  volatile  acid  should,  in  general,  not  be  over  0.12  to  0.16 
per  cent,  depending  upon  the  age  of  the  wine.  A  wine  properly 
made  should  not  have  the  volatile  acid,  estimated  as  acetic,  ex- 
ceed one-fourth  of  the  total  free  acid,  calculated  as  tartaric. 

Coloring  Matters:  Detection  of  Coal-tar  Dyes.j  —  Fifty  c.c. 
of  the  sample  are  diluted  to  100  c.c.  with  water,  filtered  if  neces- 

*  /.  hid.  Eng.  Chem.,  1910,  31. 

t  Sostegni  and  Carpentieri:  Zlschr.  anal.  Chem.,  35,  i8g6,  397. 


ANALYTICAL   METHODS  1 95 

sary,  faintly  acidified  with  hydrochloric  or  acetic  acid,  and  a 
piece  of  white  woolen  cloth,  which  has  been  thoroughly  washed 
with  hot  water,  is  immersed  in  the  solution  and  boiled  for  five  to 
ten  minutes.  The  cloth  is  then  removed  and  thoroughly  washed 
with  boiling  water,  and  boiled  in  a  dilute  solution  of  ammonia 
(i  :  50).  With  some  of  the  dyes  the  color  is  stripped  from  the 
wool  quite  readily;  with  others  it  is  necessary  to  boil  for  some 
time.  The  wool  is  removed,  the  ammoniacal  solution  made 
faintly  acid  with  hydrochloric  acid,  and  another  piece  of  white 
wool  is  immersed  and  again  boiled.  This  second  dyeing  fixes 
coal-tar  dyes  on  the  fibre,  but  fruit  and  vegetable  colors  remain 
on  the  first  piece  of  wool. 

Notes.  —  It  is  absolutely  necessary  that  the  second  dyeing 
should  be  made,  as  some  of  the  coal-tar  dyes  will  dye  a  dirty 
orange  in  the  first  acid  bath  which  might  be  easily  passed  for 
vegetable  color  but  on  treatment  in  alkaline  bath  and  second 
acid  bath  becomes  a  bright  pink. 

Excess  of  acid  should  be  avoided  since  some  of  the  colors  do 
not  dye  readily  in  strongly  acid  solution. 

Another  advantage  in  the  second  dyeing  is  that  if  a  large 
piece  of  woolen  cloth  is  used  in  the  first  dyeing,  and  a  small 
piece  in  the  second  dyeing,  small  amounts  of  coloring  matter 
can  be  brought  out  much  more  decidedly  in  the  second  dyeing, 
where  practically  all  of  the  vegetable  coloring  matter  has  been 
excluded. 

Several  colors  which  are  not  coal-tar  dyes,  notably  archil  and 
archil  derivatives,  give  reactions  b}'  this  method  and  are  liable 
to  be  confused  with  coal-tar  colors.  For  hints  as  to  the  method 
for  detecting  these  reference  may  be  made  to  Bulletin  107, 
Bureau  of  Chemistry,  page  190. 

The  further  separation  and  identification  of  the  artificial 
colors  is  too  difficult  a  matter  to  be  taken  up  here.  The  student 
is  referred  for  information  on  this  point  to  the  following:  ]\Iulli- 
ken:  The  Identification  of  Commercial  Dyestuffs;  Loomis: 
Circular  63,  Bureau  of  Chemistry;  Allen:   Commercial  Organic 


196  AIR,   WATER,   AND    FOOD 

Analysis,  4th  Ed.,  Vol.  V;  Green  and  others*:  The  Identi- 
fication of  Dyestuffs  on  Animal  Fibres. 

Preservatives.  —  The  preservatives  to  be  sought  generally  in 
wines  are  salicylic  and  benzoic  acids  and  their  salts.  Sulphurous 
acid  and  sulphites  are  also  used.  For  methods  of  detecting 
other  substances  less  commonly  employed,  such  as  abrastol,  beta- 
naphthol,  etc.,  reference  may  be  made  to  Bulletin  107  of  the 
Bureau  of  Chemistry.  Boric  acid  is  occasionally  used,  but  since 
a  small  amount  of  it  is  normally  present  in  wines,  tests,  to  be 
of  value,  should  be  quantitative. 

Salicylic  Acid.  — Acidify  about  50  c.c.  of  the  wine  with  5  c.c. 
of  dilute  (i  :  3)  sulphuric  acid  and  extract  in  a  separatory  fun- 
nel with  25  c.c.  of  ether.  Draw  off  the  lower  layer,  wash  the 
ether  twice  with  water,  using  10  c.c.  each  time  and  finally  evapo- 
rate the  ether  in  a  porcelain  dish  at  room  temperature.  To  the 
residue  in  the  dish  add  2  to  3  drops  of  very  dilute  ferric  chloride 
or  better  ferric  alum  solution  (App.  B).  A  deep  purple  or  violet 
color  indicates  salicylic  acid. 

Notes.  —  Not  more  than  50  c.c.  should  be  used  for  the  test, 
since  a  trace  of  salicylic  acid  seems  normally  present  in  some 
wines. 

The  washing  with  water  is  to  free  the  ether  from  traces  of 
sulphuric  acid  which  interferes  with  the  development  of  the 
violet  color. 

Care  should  be  exercised  in  making  the  extraction  with  ether 
not  to  shake  the  separatory  funnel  too  violently,  since  a  trouble- 
some emulsion  may  result. 

Benzoic  Acid.\  —  Acidify  about  100  c.c.  of  wine  with  sulphuric 
acid,  extract  with  ether,  and  evaporate  the  ethereal  solution  as 
in  the  detection  of  salicyKc  acid.  Treat  the  residue  with  2  or 
3  c.c.  of  strong  sulphuric  acid.  Heat  till  white  fumes  appear; 
organic  matter  is  charred  and  benzoic  acid  is  converted  into 
sulpho-benzoic  acid.  A  few  crystals  of  ammonium  nitrate  are 
then  added.     This  causes  the  formation  of  metadinitrobenzoic 

*  /.  Soc.  Dyers  attd  Colourists,  190 j,  236. 
t  Mohler:  Bull.  Soc.  Chim.  [3],  3,  1890,  414. 


ANALYTICAL  METHODS  I97 

acid.  When  cool  the  acid  is  diluted  with  water  and  ammonia 
added  in  excess,  followed  by  a  drop  or  two  of  ammonium  sulphide. 
The  nitro-compound  becomes  converted  into  ammonium  meta- 
diamidobenzoic  acid,  which  possesses  a  red  color.  This  reaction 
takes  place  immediately,  and  is  seen  at  the  surface  of  the  liquid 
without  stirring. 

Sulphurous  Acid  and  Sulphites.  —  See  directions  under  Beer, 
page  198. 

BEER  AND    OTHER   IVLA.LT   LIQUORS 

Before  analysis  the  sample  must  be  thoroughly  shaken  in  a 
large  flask,  in  order  to  remove  carbon  dioxide. 

Specific  Gravity.  —  Taken  with  a  pyknometer  at  15.5°  C. 

Alcohol.  —  Determined  as  in  the  analysis  of  wine.  The  ad- 
dition of  calcium  carbonate  will  not  be  necessary.  If  the  sample 
foams  much  this  can  be  prevented  by  the  addition  of  about  half 
a  gram  of  tannin  before  distilling. 

Extract.  —  Determine  the  extract  content  corresponding  to 
the  specific  gravity  of  the  dealcoholized  beer  according  to  Table 
XIII.     For  this  purpose  employ  the  formula 

Sp  =  g  +  {i~g'), 

in  which  Sp  is  the  specific  gravity  of  the  dealcoholized  beer,  g 
the  specific  gravity  of  the  beer,  and  g'  the  specific  gravity  of  the 
distillate  obtained  in  the  determination  of  alcohol.  Instead  of 
using  this  formula  the  residue  from  the  distillation  of  alcohol  is 
sometimes  diluted  to  the  original  volume,  and  its  specific  grax'ity 
taken.  This  is  often  impracticable  owing  to  the  necessity  of 
employing  tannic  acid  to  prevent  foaming  in  the  distilling  flask, 
and  owing  to  the  coagulation  of  proteids  during  the  distillation. 

Note.  — •  The  extract  of  beer  cannot  be  accurately  determined 
by  evaporation  and  drying  at  the  boiling-point  of  water  because 
of  the  dehydration  of  the  maltose. 

Ash. — -Evaporate  25  c.c.  to  dryness  and  determine  as  de- 
scribed on  page  180. 

Free  Acids.  —  Heat  20  c.c.  to  incipient  boiling  to  expel  carbon 
dioxide  and  titrate  as  in  the  analysis  of  wine.     Fixed  acids,  con- 


198  AIR,   WATER,   AND   FOOD 

sisting  principally  of  lactic  and  succinic,  are  calculated  as  lactic 

N       .  . 

acid.     One  c.c.  of  — ■  sodium  hydroxide  =  0.0090  gram  of  lactic 
10 

acid. 

Reducing  Sugar.  —  Dilute  25  c.c.  of  the  beer,  freed  from  car- 
bon dioxide,  to  100  c.c.  Determine  the  reducing  sugar  in  25  c.c. 
of  this  solution  as  directed  on  page  145,  enough  water  being 
added  to  make  the  total  volume  of  the  Fehling's  solution-sugar 
mixture  100  c.c.  Express  the  results  in  terms  of  maltose,  as 
given  in  Table  XII. 

Preservatives.  —  The  preservatives  most  commonly  employed 
in  beer  are  benzoic  and  salicylic  acids  and  their  sodium  salts, 
sulphites  and  fluorides. 

Benzoic  and  Salicylic  Acids.  —  Detected  as  described  under 
Wine. 

Sulphites.  —  Qualitative  Test.  —  Use  an  apparatus  similar  to 
that  described  for  the  determination  of  volatile  acids  in  wine. 
To  50  c.c.  of  the  sample  add  about  a  gram  of  sodium  bicarbonate, 
20  c.c.  of  20  per  cent  phosphoric  acid,  and  immediately  con- 
nect the  flask  with  the  condenser.  Pass  steam  through  the 
flask  until  about  20  c.c.  have  collected  in  the  distillate.  To  the 
distillate  add  bromine  water  in  slight  excess  and  boil.  Expel 
the  excess  of  bromine  and  test  for  sulphuric  acid  with  hydro- 
chloric acid  and  barium  chloride  in  the  usual  manner. 

Notes.  —  The  method  described  does  not  distinguish  between 
free  sulphurous  acid  and  that  present  in  the  form  of  sulphites. 
The  former  can  be  distilled  without  the  addition  of  phosphoric 
acid. 

The  presence  of  sulphites  in  a  sample  should  not  be  con- 
sidered e\idence  of  added  preservatives  unless  an  excessive 
amount  is  found,  since  the  use  of  sulphured  malt  or  hops  may 
introduce  a  small  amount.  To  obtain  conclusive  data,  a  quan- 
titative determination  of  the  amount  present  should  be  made. 

This  can  be  done  by  a  method  similar  to  that  used  for  its 
detection,  distilling  in  a  current  of  carbon  dioxide,  absorbing 
the  sulphur  dioxide  in  bromine  water  and  determining  the  re- 


ANALYTICAL   METHODS  199 

suiting  sulphuric  acid  as  barium  sulphate.  In  the  case  of  food 
products,  where  sulphides  are  liable  to  be  present  also,  the  steam 
should  pass  through  a  solution  of  copper  sulphate*  before  en- 
teriiog  the  condenser  in  order  to  remove  any  hydrogen  sulphide 
formed  by  the  action  of  the  phosphoric  acid.  Details  of  the 
method  will  be  found  in  Leach's  Food  Analysis. 

In  Bulletin  107  it  is  recommended  to  distill  into  a  standard 
iodine  solution  and  titrate  the  excess  of  iodine.  This  has  the 
disadvantage,  however,  that  other  iodine-reducing  substances 
than  sulphurous  acid  may  pass  into  the  distillate  and  give  too 
high  results. 

Fluorides.  —  The  well-known  cjualitative  test  for  fluorides  by 
etching  a  glass  plate  may  be  modified  by  the  use  of  a  suitable 
condenser  and  made  sufficiently  delicate  to  be  used  here.  It  is 
possible  also  by  suitable  regulation  of  the  temperature  to  make 
the  test  approximately  quantitative.! 

Flavoring  Extracts 

The  work  on  alcoholic  liquids  can  be  pleasantly  varied  by 
substituting  for  it,  in  some  cases,  the  determination  of  alcohol 
and  other  important  components  of  the  usual  flavoring  essences', 
the  most  important  of  which  are  vanilla  and  lemon.  Several 
important  types  of  analytical  methods,  such  as  the  determina- 
tion of  essential  oils  and  quantitative  extraction  with  volatile 
solvents,  are  also  brought  to  the  attention  of  the  student. 

VANILLA 

Vanilla  extract  is  a  dilute  alcoholic  tincture  of  the  vanilla 
bean,  the  fruit  of  a  climbing  plant  of  the  orchid  family.  The 
best  grades  are  made  by  allowing  the  cut  and  bruised  beans  to 
macerate  in  the  alcohol  for  several  months,  the  liquid  thus 
obtained  being  deep  brown  in  color,  with  a  delightful  perfume 
and  flavor.  Sugar  is  added  to  assist  in  the  extraction  and  to 
sweeten  the  product. 

*  Winton  and  Bailey:  J .  Am.  Chcm.  Soc,  igoy,  1499. 

t  Woodman  and  Talbot:   /.  Am.  Chem.  Soc,  igo6,  1437;   1907,  1362. 


200 


AIR,  WATER,  AND   FOOD 


The  cost  of  a  quart  of  the  pure  extract,  according  to  Winton,* 
is  from  about  60  cents  to  $2.50,  depending  chiefly  upon  the 
grade  of  beans  used. 

The  composition  of  five  pure  vanilla  extracts,  made  from 
beans  of  different  grades,  is  given  in  the  following  table,t  the 
results  being  expressed  in  per  cent  by  weight: 


Grade  of  bean. 

Specific 
gravity. 

Vanillin. 

Alcohol. 

Total 
residue. 

Cane- 
sugar. 

Mexican  (whole) 

Mexican  (cut) 

South  American  (whole) . 

Bourbon  (whole) 

Tahiti  (whole) 

I. 0159 
I. 0146 
I . 1009 
I. 0166 
I .0104 

0.125 
0.065 
0.215 
0.138 
0.108 

37-96 
39-92 
38.58 
38-32 
38-84 

22.60 
23.10 
22.00 
23-13 
21-75 

19.90 
19.20 
19.00 
20.40 
20.00 

The  adulteration  of  vanilla  extract  consists  principally  in  the 
use  of  extract  of  Tonka  bean,  a  cheap  substitute  somewhat  re- 
sembling vanilla  in  its  flavor,  in  the  use  of  artificial  prepara- 
tions of  the  active  principles  of  vanilla  and  tonka,  vanillin  and 
coumarin,  and  in  the  addition  of  artificial  color,  usually  cara- 
mel. A  cheap  extract  may  be  entirely  an  artificial  mixture, 
made  of  artificial  vanillin  or  coumarin,  or  both,  in  weak  alcohol, 
colored  with  caramel.  An  occasional  adulteration  is  the  use  of 
alkali,  such  as  potassium  bicarbonate,  to  hold  the  resin  in  solu- 
tion and  permit  the  use  of  a  more  dilute  alcohol. 

An  extract  of  vanilla  of  good  quality  should  contain  from  25 
to  40  per  cent  of  alcohol,  from  o.io  to  0.20  per  cent  of  vanillin, 
and  give  a  good  precipitate  of  vanilla  resins.  Imitation  extracts 
usually  show  one  or  several  of  the  following  characteristics: 
Presence  of  coumarin;  deficiency  in  resins;  abnormally  low  or 
high  content  of  vanillin;  presence  of  artificial  color;  low  lead 
number. 

Analytical  Methods.  —  Alcohol.  —  Measure  25  c.c.  of  the 
sample,  add  100  c.c.  of  water,  and  determine  the  alcohol  by 

*  Conn.  Agr.  Exp.  Sta.  Report,  igoi,  150. 
t  Conn.  Agr.  Exp.  Sta.  Report,  igoi,  150. 


ANALYTICAL  METHODS  20I 

volume,  as  directed  on  page  191,  omitting  the  use  of  calcium 
carbonate  and  tannic  acid. 

Vanillin  and  Coumarin.  —  (Modified  method  of  Hess  and 
Prescott).*  Weigh  50  grams  into  a  250-c.c.  beaker  with  marks 
showing  volumes  of  80  c.c.  and  50  c.c,  dilute  to  80  c.c,  and 
evaporate  to  50  c.c.  in  a  water-bath  kept  at  70°  C.  Dilute  again 
to  80  c.c.  and  evaporate  to  50  c.c.  Transfer  to  a  loo-c.c.  flask, 
rinsing  out  the  beaker  with  hot  water,  add  25  c.c.  of  lead  acetate 
solution  (80  grams  of  neutral  lead  acetate  made  up  to  a  liter), 
make  up  to  the  mark  with  water,  shake  and  allow  it  to  stand 
over  night.  Decant  on  a  small  dry  filter,  pipette  off  50  c.c.  of 
the  filtrate,  and  extract  it  four  times  in  a  separatory  funnel, 
using  15  c.c.  of  ether  each  time. 

Combine  the  ether  extracts  in  another  separatory  funnel  and 
wash  five  times  wdth  2  per  cent  ammonium  hydroxide,  using 
10  c.c.  the  first  time  and  5  c.c.  for  each  subsequent  shaking.  Set 
aside  the  combined  ammoniacal  solutions  for  the  determination 
of  vanillin. 

Transfer  the  ether  solution  to  a  weighed  dish  and  allow  the 
ether  to  evaporate  at  room  temperature.  Dry  in  a  desiccator 
over  sulphuric  acid  and  weigh.  If  the  residue  is  not  white  and 
crystalline  stir  it  for  fifteen  minutes  with  15  c.c.  of  petroleum 
ether  (boiling  point  30°  to  40°  C.)  and  decant  the  clear  liquid  into 
a  beaker.  Repeat  the  treatment  with  petroleum  ether  two  or 
three  times.  Allow  the  residue  to  stand  in  the  air  until  ap- 
parently dry,  completing  the  drying  in  the  desiccator.  Weigh, 
and  deduct  the  weight  from  the  weight  of  the  residue  obtained 
after  the  ether  evaporation,  thus  obtaining  the  weight  of  the 
coumarin.  This  may  be  recognized  by  its  characteristic  odor, 
resembling  that  of  "sweet  grass,"  and  by  Leach's  testf  as 
follows:    Dissolve    the  residue   in  a  few  drops   of   hot  water, 

N  .     . 
and  add  one  or  two  drops  of  —  iodine  in  potassium  iodide. 

10 

On  stirring  with  a  rod,  a  brown  precipitate  will  form,  which 

*  /.  Atn.  Chem.  Soc,  igo^,  719;   Bur.  of  C hem.,  Bull.  137,  68. 
t  Leach:  "Food  Inspection  and  Analysis,"  3d  Ed.,  p.  867. 


202  AIR,  WATER,  AND  FOOD 

will  gather  into  dark  green  flocks.  The  reaction  is  especially 
marked  if  carried  out  in  a  white  porcelain  crucible  or  dish. 

Slightly  acidulate  the  ammoniacal  solution  reserved  for  vanillin 
with  lo  per  cent  hydrochloric  acid.  Cool,  and  shake  out  in  a 
separatory  funnel  with  four  portions  of  ether,  as  described  for 
the  first  ether  extraction.  Evaporate  the  ether  at  room  tem- 
perature in  a  weighed  dish,  dry  over  sulphuric  acid,  and  weigh 
the  vanillin. 

If  the  residue  is  white,  it  may  be  safely  assumed,  in  the  majority 
of  cases,  that  it  is  pure  vanillin.  If  dark  colored,  however,  the 
dry  residue  should  be  extracted  not  less  than  fifteen  times  with 
boiling  petroleum  ether  (boiling  point  40°  C.  or  below) .  Evapo- 
rate the  solvent,  dry  and  weigh  the  vanillin.  A  small  amount 
of  the  residue,  dissolved  in  two  drops  of  concentrated  hydro- 
chloric acid,  should  give  a  pink  color  upon  the  addition  of  a 
crystal  of  resorcin. 

Notes.  —  The  separation  of  vanillin  and  coumarin  is  based 
on  the  differences  in  their  chemical  constitution.  VaniUin  is 
hydroxymethoxybenzoic  aldehyde,  while  coumarin  is  the  anhy- 
dride of  orthohydroxycinnamic  acid.  On  account  of  the  alde- 
hydic  nature  of  the  vanillin,  the  separation  by  dilute  ammonia 
is  possible,  the  aldehyde  ammonia  compound  of  vanillin  being 
readily  soluble  in  water,  while  the  coumarin  remains  wholly  in 
the  ether. 

If  a  portion  of  the  vanilHn,  after  weighing,  be  dissolved  in  two 
or  three  drops  of  ether  and  allowed  to  evaporate  spontaneously 
on  a  microscope  sHde  it  shows  a  characteristic  appearance  with 
polarized  light.  The  vanillin  crystallizes  in  slender  needles, 
forming  star-shaped  clusters.  These  give  a  brilliant  play  of 
colors  with  crossed  Nicols,  even  without  the  selenite  plate. 

Normal  Lead  Number.  —  To  a  lo-c.c.  portion  of  the  filtrate 
obtained  from  the  lead  acetate  in  the  determination  of  vanillin 
and  coumarin  add  25  c.c.  of  water,  sulphuric  acid  in  slight  excess, 
and  100  c.c.  of  95  per  cent  alcohol,  let  stand  over  night,  filter  on  a 
Gooch  crucible,  wash  with  alcohol,  dry  in  the  oven  of  the  water- 
bath,  ignite  for  three  minutes  at  low  redness,  taking  care  to 


ANALYTICAL  METHODS  203 

avoid  the  reducing  flame,  and  weigh  the  lead  sulphate.  Cal- 
culate the  normal  lead  number  by  the  following  formula 

p  ^  100  X  0.6831  {S  -  W) 
5 

in  which  P  =  normal  lead  number,  5  =  grams  of  lead  sulphate 

corresponding  to  2.5  c.c.  of  the  lead  acetate  solution,  as  deter- 
mined from  a  blank  analysis,  and  W  =  grams  of  lead  sulphate 
obtained  in  10  c.c.  of  the  filtrate,  as  just  described. 

Note.  —  The  normal  lead  number  of  genuine  vanilla  extracts 
determined  by  this  method  ranges  from  0.35  to  0.60.  Artificial 
extracts  generally  are  distinctly  lower,  sometimes  as  low  as  0.03, 

More  accurate  results  can  be  obtained  by  regulating  more 
closely  the  time  and  temperature  during  the  standing  of  the  so- 
lution with  lead  acetate.  Winton  and  Berry*  recommend  stand- 
ing 18  hours  at  37°  to  40°  C.  They  find  that,  determined  in  this 
manner,  the  minimum  normal  lead  number  for  vanilla  extracts 
prepared  according  to  the  U.  S.  Pharmacopoeia  is  0.40. 

Resins.  —  Evaporate  25  or  50  c.c.  of  the  extract  to  one-third 
its  volume  on  the  water-bath  in  order  to  remove  the  alcohol. 
Make  up  to  the  original  volume  with  hot  water.  If  no  alkali 
has  been  used  in  the  manufacture  of  the  extract,  the  resin 
should  appear  at  this  point  as  a  flocculent  brown  residue.  Add 
acetic  acid  in  slight  excess,  allow  the  evaporating-dish  to  stand 
in  a  warm  place  for  a  time  to  separate  the  resin  completely, 
and  filter.  Wash  the  residue  on  the  filter,  and  save  both  the 
filtrate  and  residue.  Test  the  resin  by  placing  pieces  of  the 
filter,  with  the  resin  attached,  in  a  few  cubic  centimeters  of 
dilute  caustic  potash.  The  resin  is  dissolved  with  a  deep  red 
color,  and  on  acidifying  is  again  precipitated.  Test  the  filtrate 
by  adding  to  it  a  few  drops  of  basic  lead  acetate.  A  bulky  pre- 
cipitate is  formed,  on  account  of  the  organic  acid,  gums,  etc., 
present. 

Confirm  the  resin  test  by  shaking  5  c.c.  portions  of  the  ex- 
tract in  separate  test-tubes  with   10  c.c.  of  amyl  alcohol  and 

*  Bur.  of  C hem.,  Bull.  137,  120. 


204  AIR,  WATER,  AND   FOOD 

lo  c.c.  of  ether.  With  pure  extracts  the  upper  layers  will  be 
colored,  varying  from  light  yellow  to  deep  brown;  with  artificial 
extracts,  free  from  resin,  the  amyl  alcohol  and  ether  layers  will 
be  uncolored. 

Note.  —  While  the  artificial  vanillin,  as  sold  on  the  market 
and  used  in  the  manufacture  of  low-grade  extracts,  is  identical 
with  the  vanillin  of  the  vanilla  bean,  it  is  true  that  pure  extracts 
owe  their  value  and  flavor  to  other  ingredients  as  well  as  to  the 
vanillin  present.  Among  these  "extractive  matters"  the  resins 
are  important  from  an  analytical  standpoint,  serving  by  their 
presence  or  absence  to  determine  whether  true  vanilla  is  present 
or  the  extract  entirely  artificial.  As  a  quick  and  ready  test, 
serving  to  distinguish  artificial  extracts  from  genuine  prepara- 
tions of  the  vanilla  bean,  the  amyl  alcohol  and  ether  tests  will 
be  found  especially  useful. 

Color :  Caramel.  —  Caramel  is  the  color  commonly  used  in 
vanilla  extracts,  although  coal-tar  dyes  have  been  found.  The 
presence  of  dyes  is  sometimes  indicated  by  the  color  of  the 
amyl  alcohol  in  testing  for  the  resin,  they  being  in  many  cases 
soluble  in  amyl  alcohol,  but  insoluble  in  ether. 

Lead  Acetate  Test.  —  The  coloring  matter  present  in  vanilla 
extracts  is  almost  completely  removed  when  the  dealcoholized 
extract  is  treated  with  a  few  cubic  centimeters  of  basic  lead 
acetate  solution.  When  caramel  is  present,  the  filtrate  and 
precipitate,  if  any,  have  the  characteristic  red-brown  color  of 
caramel. 

Marsh  Test.*  —  Evaporate  25  c.c.  of  the  extract  until  the  odor 
of  alcohol  is  no  longer  apparent  and  the  liquid  is  reduced  to  a 
thick  sirup.  Dissolve  the  residue  in  water  and  alcohol,  using 
26.3  c.c.  of  95  per  cent  alcohol,  and  making  up  to  volume  in  a 
50-c.c.  flask  with  water.  Transfer  25  c.c.  of  this  solution  to  a 
separatory  funnel;  add  25  c.c.  of  the  Marsh  reagent  and  shake, 
not  too  vigorously,  to  avoid  emulsification.  Allow  the  layers 
to  separate  and  repeat  the  shaking  twice  more.  After  the 
layers  have  separated  clearly,  run  off  the  lower  layer  into  a  25-c.c. 

*  Bur.  of  Chem.,  Bull.  152,  p.  149. 


ANALYTICAL   METHODS  205 

cylinder,  and  make  up  to  volume  with  50  per  cent  (by  volume) 
alcohol.  Filter  if  necessary  and  compare  in  a  colorimeter  with 
the  remaining  25-c.c.  portion  (which  has  not  been  extracted  with 
the  reagent)  and  express  the  results  as  per  cent  of  color  insolu- 
ble in  amyl  alcohol. 

The  Marsh  reagent  is  prepared  as  follows:  Mix  100  c.c.  of 
amyl  alcohol,  3  c.c.  of  sirupy  phosphoric  acid,  and  3  c.c.  of  water; 
shake  before  using.  If  the  reagent  becomes  colored  on  standing, 
the  amyl  alcohol  should  be  redistilled  over  5  per  cent  phosphoric 
acid. 

Note.  —  The  method  is  based  on  the  greater  solubility  in  acid 
amyl  alcohol  of  the  natural  color  of  the  vanilla  bean  as  com- 
pared with  caramel.  A  genuine  extract,  uncolored  with  caramel, 
will  not  usually  show  more  than  40  per  cent  of  color  insoluble  in 
amyl  alcohol. 

LEMON 

Lemon  extract  is  usually  made  by  dissolving  oil  of  lemon, 
obtained  by  expression  or  distillation  from  the  rind  of  the  lemon, 
in  strong  alcohol.  The  product  is  sometimes  colored  with  the 
color  of  lemon  peel.  The  Federal  standards  *  require  a  content 
of  lemon  oil  of  at  least  5  per  cent  by  volume.  The  expensive 
ingredient  of  the  extract  is  the  alcohol,  since  alcohol  of  at  least 
80  per  cent  strength  by  volume  must  be  used  to  dissolve  5  per 
cent  of  lemon  oil;  hence  in  making  cheap  extracts  the  manu- 
facturer endeavors  to  use  a  dilute  alcohol,  even  under  the  neces- 
sity of  omitting  a  portion  or  all  of  the  oil  of  lemon. 

The  common  forms  of  adulteration  of  lemon  extract  are  the 
use  of  weak  alcohol  and  consequent  deficiency  of  lemon  oil,  as 
already  noted ;  the  substitution  for  the  lemon  oil  of  small  amounts 
of  stronger  oils,  as  oil  of  citronclla,  oil  of  lemon-grass,  and  the 
like;  the  use  of  citral,  the  odorous  principle  of  lemon  oil,  used 
for  making  the  so-called  "terpencless  lemon  extracts;"  and  the 
coloring  of  the  extracts  by  coal-tar  colors  or  turmeric. 

Preliminary  Test.  —  To  a  little  of  the  extract  in  a  test-tube 
add  seven  or  eight  times  its  volume  of  water.  A  high-grade  ex- 
*  U.  S.  Dcpt.  -Agric,  OfBce  of  the  Secretary,  Circ.  19. 


206  AIR,   WATER,   AND   FOOD 

tract  will  show  a  heavy  cloud,  due  to  the  precipitation  of  the 
lemon  oil.  If  no  cloudiness  or  turbidity  appears  it  may  be  safely 
inferred  that  no  oil  is  present. 

Alcohol.  —  The  determination  of  alcohol  is  somewhat  com- 
plicated in  this  case  by  the  presence  of  the  volatile  oil  of  lemon 
which  must  be  removed  before  distilling. 

Dilute  20  c.c.  of  the  extract  to  100  c.c.  with  water,  and  pour 
the  mixture  into  a  dry  Erlenmeyer  flask  containing  5  grams  of 
light  magnesium  carbonate.  Shake  thoroughly  and  filter 
through  a  dry  filter.  Measure  50  c.c.  of  the  clear  filtrate,  add 
about  15  c.c.  of  water,  and  distill  50  c.c,  as  directed  on  page  191. 
From  the  specific  gravity  of  the  distillate  determine  the  per  cent 
of  alcohol  by  volume,  and  this,  multiplied  by  5,  will  give  the 
percentage  in  the  original  extract. 

Note.  —  The  magnesia  serves  to  absorb  the  precipitated  oil 
and  prevent  it  from  passing  through  the  filter. 

Lemon  Oil.  —  Pipette  20  c.c.  of  the  extract  into  a  Babcock 
milk  bottle;  add  i  c.c.  dilute  hydrochloric  acid  (i  :  i);  then 
add  from  25  to  28  c.c.  of  w'ater  previously  warmed  to  60°  C; 
mix  and  let  stand  in  water  at  60°  for  five  minutes;  whirl  in 
centrifuge  for  five  minutes;  fill  with  warm  water  to  bring  the 
oil  into  the  graduated  neck  of  the  flask;  repeat  whirling  for 
two  minutes;  stand  the  flask  in  water  at  60°  C.  for  a  few  min- 
utes and  read  the  per  cent  of  oil  by  volume.  If  the  determina- 
tion is  not  made  in  duplicate  the  flask  should  be  balanced  by 
another  containing  an  equal  weight  of  water.  In  case  oil  of 
lemon  is  present  in  amounts  over  2  per  cent  add  to  the  percent- 
age of  oil  found  0.4  per  cent  to  correct  for  the  oil  retained  in 
solution.  If  less  than  2  per  cent  and  more  than  i  per  cent  is 
present,  add  0.3  per  cent  for  correction. 

Color.  —  Test  for  coal-tar  colors  by  evaporating  a  portion  of 
the  extract  to  dryness  on  the  water-bath.  Dissolve  the  residue 
in  water  and  carry  out  the  double  dyeing  method,  as  described 
on  page  194. 

It  may  be  advisable  not  to  add  any  acid  to  the  dye  bath,  as 
Naphthol  Yellow  S,  which  is  commonly  used  in  lemon  extracts, 
dyes  wool  best  from  a  nearly  neutral  bath. 


ANALYTICAL  METHODS  207 

To  test  for  turmeric  add  to  a  portion  of  the  sample  three 
drops  of  saturated  boric  acid  solution,  one  Sfnall  drop  of  dilute 
(i  :  10)  hydrochloric  acid,  and  a  piece  of  filter-paper  so  ar- 
ranged that  it  is  only  half  immersed  in  the  liquid.  Evaporate 
to  dryness  on  the  water-bath.  In  the  presence  of  turmeric  the 
paper  will  be  colored  pink  and  the  test  may  be  confirmed  as 
described  on  page  154.  Excess  of  hydrochloric  acid  should  be 
avoided  as  in  testing  for  boric  acid. 

To  show  the  presence  of  natural  color  derived  from  lemon 
peel  the  following  reactions  will  be  found  helpful:*  Dilute  a  few 
cubic  centimeters  of  the  extract  until  the  color  has  nearly  dis- 
appeared and  divide  the  solution  between  two  test-tubes.  To 
one  add  a  few  drops  of  concentrated  hydrochloric  acid  and  to 
the  other  a  few  drops  of  strong  ammonia.  In  the  presence  of 
natural  color  a  distinct  yellow  color  should  result  in  each  case. 

Citral.  —  See  Bur.  of  C hem.,  Bull.  137,  70. 

*  Albrech:  Bur.  oj  Chem.,  Bull.  137,  71. 


APPENDICES 


APPENDIX  A 


TABLE    I 


TENSION  OF  AQUEOUS  VAPOR  IN  MILLIMETERS  OF  MERCURY  FROM  O     TO  3O.9     C. 
REDUCED   TO   0°   AND   SEA-LEVEL 


0.0 

0.1 

0.2 

0.3 

0.4 

0.5 

0.6 

0.7 

0.8 

0.9 

0° 

4-57 

4.60 

4.64 

4.67 

4.70 

4.74 

4.77 

4.80 

4.84 

4.87 

I 

4 

91 

4 

94 

4.98 

5.02 

5.05 

5.09 

5.12 

5-16 

5.20 

5.23 

2 

S 

27 

5 

31 

5-35 

5-39 

5-42 

5  46 

5-50 

5-54 

5.58 

5.62 

3 

5 

66 

S 

70 

5-74 

5.78 

5-82 

5-86 

5-9° 

5-94 

5. 99 

6.03 

4 

6 

07 

6 

II 

6. IS 

6.20 

6.24 

6.28 

6.33 

6.37 

6.42 

6.46 

5 

6 

51 

6 

55 

6.60 

6.64 

6.69 

6.74 

6.78 

6.83 

6.88 

6.92 

6 

6 

97 

7 

02 

7.07 

7.12 

7.17 

7.22 

7.26 

7.31 

7-36 

7.42 

7 

7 

47 

7 

52 

7-57 

7.62 

7.67 

7.72 

7-78 

7.83 

7.88 

7.94 

8 

7 

99 

8 

05 

8.10 

8.15 

8.21 

8.27 

8.32 

8.38 

8.43 

8.49 

9 

8 

55 

8 

61 

8.66 

8.72 

8.78 

8.84 

8.90 

8.96 

9.02 

9.08 

10 

9 

14 

9 

20 

9.26 

9.32 

9.39 

9.45 

9-51 

9.58 

9-64 

9.70 

II 

9 

77 

9 

83 

9.90 

9.96 

10.03 

10.09 

10.16 

10.23 

10.30 

10.36 

12 

10 

43 

10 

50 

10. S7 

10.64 

10.71 

10.78 

10.85 

10.92 

10.99 

11.06 

13 

II 

14 

II 

21 

XI.  28 

11.36 

11.43 

11.50 

11.58 

11.66 

11.73 

II. 81 

14 

II 

88 

II 

96 

12.04 

12.12 

12.19 

12.27 

12.35 

12.43 

12.51 

12.59 

15 

12 

67 

12 

76 

12.84 

12.92 

13.00 

13.09 

13.17 

13.25 

13.34 

13-42 

16 

13 

51 

13 

60 

13-68 

13-77 

13.86 

13-95 

14.04 

14.12 

14.21 

14.30 

17 

14 

40 

14 

49 

14.58 

14.67 

14.76 

14.86 

14.95 

IS -04 

1S-14 

15.23 

18 

IS 

33 

15 

43 

1552 

15.62 

15-72 

15.82 

15-92 

16.02 

16.12 

16.22 

19 

16 

32 

16 

42 

16.52 

16.63 

16.73 

16.83 

16.94 

17.04 

17-15 

17.26 

20 

17 

36 

17 

47 

17.58 

17.69 

17.80 

17.91 

18.02 

18.13 

18.24 

18.35 

21 

18 

47 

18 

58 

18.69 

18.81 

18.92 

19.04 

19.16 

19.27 

19.39 

19.51 

22 

19 

63 

19 

75 

19.87 

19.99 

20.11 

20.24 

20.36 

20.48 

20.61 

20.73 

23 

20 

86 

20 

98 

21. II 

21.24 

21.37 

21.50 

21.63 

21.76 

21.89 

22.02 

24 

22 

15 

22 

29 

22.42 

22.55 

22.69 

22.83 

22.96 

23.10 

23.24 

23.38 

25 

23 

52 

23 

66 

23.80 

23-94 

24.08 

24-23 

24-37 

24.52 

24.66 

24.81 

26 

24 

96 

25 

10 

25.25 

25  40 

25.55 

25.70 

25.86 

26.01 

26.16 

26.32 

27 

26 

47 

26 

63 

26.78 

26.94 

27.10 

27.26 

27-42 

27.58 

27.74 

27.90 

28 

28 

07 

28 

23 

28.39 

28.56 

28.73 

28.89 

29.06 

29.23 

29.40 

29.57 

29 

29 

74 

29 

92 

30.09 

30.26 

30.44 

30.62 

30.79 

30.97 

31.15 

31-33 

30 

31 

51 

31 

69 

31.87 

32.06 

32.24 

32.43 

32.61 

32.80 

32.99 

33-18 

208 


APPENDIX   A 


209 


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APPENDIX   A 


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APPENDIX   A 


21 


TABLE  VII 

SULPHATES   IN    WATER 

(Reduced  from  table  in  article  by  H.  F.  Muer,  J.  Ind.  Eng.  Chem.,  191 1, 

Vol.  3,  p.  553) 


Depth, 

SO3,  pts.  per 

Depth, 

SO3,  pts.  per 

Depth, 

SOj,  pts.  per 

Depth, 

so,,  pts.  per 

cm. 

million. 

cm. 

million. 

cm. 

million. 

cm. 

million. 

i-S 

3130 

6.7 

72.0 

II. 9 

47-3 

17.1 

37-3 

6 

280.0 

6 

8 

71 

3 

12.0 

47 

.0 

17.2 

37 

3 

7 

250.0 

6 

9 

70 

5 

12. I 

46 

.8 

17-3 

37 

0 

8 

238.0 

7 

0 

69 

8 

12.2 

46 

•5 

174 

36 

8 

9 

225.0 

7 

I 

69 

0 

12.3 

46 

•3 

175 

36 

8 

2 

0 

213.0 

7 

2 

68 

3 

12.4 

46 

0 

17.6 

36 

5 

2 

I 

200.0 

7 

3 

67 

S 

12.5 

45 

8 

17.7 

36 

3 

2 

2 

190.0 

7 

4 

66 

8 

12.6 

45 

5 

17.8 

36 

0 

2 

3 

183.0 

7 

S 

66 

0 

12.7 

45 

3 

17.9 

36 

0 

2 

4 

1750 

7 

6 

65 

3 

12.8 

45 

0 

18.0 

35 

8 

2 

5 

168.0 

7 

7 

64 

8 

12.9 

44 

8 

18. 1 

35 

8 

2 

6 

163.0 

7 

8 

64 

0 

13.0 

44 

5 

18.2 

35 

5 

2 

7 

158.0 

7 

9 

63 

5 

13    I 

44 

3 

18.3 

35 

3 

2 

8 

1530 

8 

0 

62 

8 

13.2 

44 

0 

18.4 

35 

3 

2 

9 

148.0 

8 

I 

62 

3 

133 

43 

8 

18.5 

35 

0 

3 

0 

143  0 

8 

2 

61 

8 

134 

43 

5 

18.6 

35 

0 

3 

I 

138.0 

8 

3 

61 

0 

135 

43 

3 

18.7 

34 

8 

3 

2 

1350 

8 

4 

60 

5 

13.6 

43 

3 

18.8 

34 

5 

3 

3 

130.0 

8 

5 

60 

0 

13-7 

43 

0 

18.9 

34 

S 

3 

4 

128.0 

8 

6 

59 

5 

13-8 

42 

8 

19.0 

34 

3 

3 

5 

125.0 

8 

7 

59 

0 

13-9 

42 

5 

19. 1 

34 

3 

3 

6 

122.5 

8 

8 

58 

5 

14.0 

42 

5 

19.2 

34 

0 

3 

7 

120.0 

8 

9 

58 

0 

14.1 

42 

3 

193 

33 

8 

3 

8 

II7-5 

9 

0 

57 

5 

14.2 

42 

0 

19.4 

33 

8 

3 

9 

115. 0 

9 

I 

57 

0 

14-3 

41 

8 

19-5 

33 

5 

4 

0 

112. 5 

9 

2 

56 

5 

14.4 

41 

5 

19.6 

33 

5 

4 

I 

110. 0 

9 

3 

56 

3 

14-5 

41 

5 

19.7 

33 

3 

4 

2 

107-5 

9 

4 

55 

8 

14.6 

41 

3 

19.8 

33 

0 

4 

3 

105.0 

9 

5 

55 

3 

147 

41 

0 

19.9 

33 

0 

4 

4 

102.5 

9 

6 

54 

8 

14.8 

40 

8 

20.0 

32 

8 

4 

5 

100. 0 

9 

7 

54 

5 

14.9 

40 

5 

20.1 

32 

5 

4 

6 

98.3 

9 

8 

54 

0 

150 

40 

5 

20.2 

32 

5 

4 

7 

96 -5 

9 

9 

53 

8 

151 

40 

3 

20.3 

32 

3 

4 

8 

94.8 

10 

0 

53 

3 

15-2 

40 

0 

20.4 

32 

0 

4 

9 

93  0 

10 

I 

52 

8 

153 

40 

0 

20.5 

32 

0 

5 

0 

91   5 

10 

2 

52 

5 

iS-4 

39 

8 

20.6 

31 

8 

5 

I 

90.0 

10 

3 

52 

3 

iSS 

39 

8 

20.7 

31 

5 

5 

2 

88.5 

10 

4 

51 

8 

15-6 

39 

5 

20.8 

31 

S 

5 

3 

873 

10 

5 

51 

5 

iS-7 

39 

3 

20.9 

31 

3 

5 

4 

85.8 

10 

6 

51 

0 

15-8 

39 

3 

21.0 

31 

3 

5 

5 

845 

10 

7 

50 

8 

159 

39 

0 

21 . 1 

31 

0 

5 

6 

83.3 

10 

8 

50 

5 

16.0 

39 

0 

21 .2 

30 

8 

5 

7 

82.0 

10 

9 

50 

3 

16.1 

38 

8 

21-3 

30 

8 

5 

8 

81.0 

II 

0 

50 

0 

16.2 

38 

5 

21.4 

30 

5 

5 

9 

80.0 

1 1 

I 

49 

5 

16.3 

38 

5 

21-5 

30 

3 

6 

0 

78.8 

II 

2 

49 

3 

16.4 

38 

3 

21  .6 

30 

3 

6 

I 

77.8 

II 

3 

48 

8 

16. 5 

38 

3 

21.7 

30 

0 

6 

2 

76.8 

II 

4 

48 

5 

16.6 

38 

0 

21.8 

30 

0 

6 

3 

75-8 

II 

5 

48 

3 

16.7 

38 

0 

21  .9 

29 

8 

6 

4 

74.8 

II 

6 

48 

0 

15-8 

37 

8 

22.0 

29 

5 

6 

5 

73-8 

II 

7 

47 

8 

16.9 

37 

5 

6 

6 

7.VO 

II 

8 

47 

5 

17.0 

37 

5 

2l6 


AIR,  WATER,  AND   FOOD 


TABLE  VIII 

TABLE  OF   HARDNESS,   SHOWING  THE   PARTS   OF  CALCIUM   CARBONATE   (caCOa)  IN 

1,000,000   FOR   EACH   TENTH   OF   A   CUBIC   CENTIMETER 

OF   SOAP   SOLUTION    USED 


0.0 

0.1 

0.2 

0.3 

0.4 

0.5 

0.6 

0.7 

0.8 

0.9 

cu.  cm. 

cu.  cm. 

cu.  cm. 

cu.  cm. 

cu.  cm. 

cu.  cm. 

cu.  cm. 

cu.  cm. 

cu.  cm. 

cu.  cm. 

0.0 

0.0 

1.6 

3-2 

I.O 

4 

8 

6 

3 

7-9 

9-5 

II  .1 

12.7 

14-3 

15-6 

16.9 

18.2 

2.0 

19 

5 

20 

8 

22.1 

234 

24.7 

26.0 

27-3 

28.6 

29-9 

31.2 

30 

32 

5 

33 

8 

35-1 

364 

37-7 

390 

40.3 

41.6 

42.9 

44-3 

4.0 

45 

7 

47 

I 

48.6 

50.0 

51-4 

529 

54-3 

55-7 

S7-I 

58.6 

50 

60 

0 

61 

4 

62.9 

643 

65.7 

67.1 

68.6 

70.0 

71-4 

72.9 

6.0 

74 

3 

75 

7 

77.1 

78.6 

80.0 

81.4 

82.9 

84-3 

85-7 

87.1 

7.0 

88 

b 

90 

0 

91.4 

92.9 

94-3 

95-7 

97.1 

98.6 

100. 0 

101.5 

8.0 

103 

0 

104 

5 

106.0 

107.5 

109.0 

no. 5 

112. 0 

"3-5 

115. 0 

116. 5 

9.0 

118 

0 

119 

5 

121 .1 

122.6 

124. 1 

125.6 

127. 1 

128.6 

130. 1 

131. 6 

10. 0 

133 

I 

134 

6 

136. 1 

137.6 

I39-I 

140.6 

142. 1 

143-7 

145-2 

146.8 

II. 0 

148 

4 

150 

0 

151-6 

153-2 

154-8 

156.3 

157-9 

159 -5 

161. 1 

162.7 

12.0 

164 

3 

165 

9 

167.5 

169.0 

170.6 

172.2 

173-8 

175-4 

177.0 

178.6 

13.0 

180 

2 

181 

7 

183.3 

184.9 

186.5 

188. 1 

189.7 

191-3 

192.9 

194.4 

14.0 

196 

0 

197 

b 

199.2 

200.8 

202.4 

204.0 

205.6 

207.1 

208.7 

210.3 

ISO 

211 

9 

213 

5 

215. 1 

216.8 

218.5 

220.2 

221.8 

223 -5 

225.2 

226.9 

TABLE   IX 

FOR  CORRECTING  THE  SPECIFIC  GRAVITY  OF  MILK  ACCORDING  TO  TEMPERATURE 
ADAPTED   FROM   THE   TABLE   OF    VIETH 

(Temperature  in  Degrees  Centigrade) 


Specific 
gravity. 

10° 

11° 

12° 

13° 

14° 

15° 

16° 

17° 

18° 

19° 

20° 

1.025 

24.1 

24-3 

24-5 

24.6 

24.7 

24-9 

25-1 

25-3 

25-4 

25-6 

25-9 

26 

25-1 

25-2 

25-4 

25-5 

25-7 

25-9 

26.1 

26 

3 

26 

5 

26 

7 

27.0 

27 

26.1 

26.2 

26.4 

26.5 

26.7 

26.9 

27.1 

27 

4 

27 

5 

27 

7 

28.0 

28 

27.0 

27.2 

27.4 

27-5 

27.7 

27-9 

28.1 

28 

4 

28 

5 

28 

7 

29.0 

29 

28.0 

28.2 

28.4 

28.5 

28.7 

28.9 

29.1 

29 

4 

29 

5 

29 

8 

30.1 

30 

29.0 

29.1 

293 

29-5 

29.7 

29.9 

30.1 

30 

4 

30 

5 

30 

8 

3I-I 

31 

29.9 

30.1 

30.3 

30-4 

30.6 

30.9 

31.2 

31 

4 

31 

5 

31 

8 

32.2 

32 

30.9 

3I-I 

31-3 

31-4 

31-6 

31-9 

32.2 

32 

4 

32 

6 

32 

9 

33-2 

33 

318 

32.0 

32-3 

32-4 

32.6 

329 

33-2 

33 

4 

33 

6 

33 

9 

34-2 

34 

32.7 

330 

33-2 

33-4 

33-6 

33-9 

34-2 

34 

4 

34 

6 

34 

9 

35-2 

35 

33-6 

33-9 

34-1 

34-4 

34-6 

34-9 

35-2 

35 

4 

35 

6 

35 

9 

36.2 

Directions.  —  Find  the  observed  gravity  in  the  left-hand  column.  Then,  in 
the  same  line,  and  under  the  observed  temperature,  will  be  found  the  corrected 
reading. 


APPENDIX  A 


217 


TABLE   X 


PERCENTAGE  OF  ALCOHOL  FROM  THE  SPECIFIC  GRAVITY  AT 


I 

-  0  - 

D    0 

C.      ( 

hehner) 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

Sp.gr. 

alcohol 

alcohol 

Sp.gr. 

alcohol 

alcohol 

Sp.gr. 

alcohol 

alcohol 

is°.s  c. 

by 

by 

I5°.S  C. 

by 

by 

15°.S  C. 

by 

by 

weight. 

volume. 

weight. 

volume. 

weight. 

volume. 

1. 0000 

0.00 

0.00 

0.9999 

0.05 

0.07 

0.9959 

2.33 

2  93 

0.9919 

4.69 

586 

8 

O.II 

0.13 

8 

2 

39 

3 

00 

8 

4-75 

5  94 

7 

0. 16 

0.  20 

7 

2 

44 

3 

07 

7 

4.81 

6.02 

6 

0.21 

0,26 

6 

2 

50 

3 

14 

6 

4.87 

6.10 

5 

0.26 

0.33 

5 

2 

56 

3 

21 

5 

4-94 

6.17 

4 

0.32 

0.40 

4 

2 

61 

3 

28 

4 

5.00 

6.24 

3 

0.37 

0.46 

3 

2 

67 

3 

35 

3 

5.06 

6.32 

2 

0.42 

0.53 

2 

2 

72 

3 

42 

2 

5-12 

6.40 

I 

0.47 

0.60 

I 

2 

78 

3 

49 

I 

S19 

6.48 

0 

053 

0.66 

0 

2 

83 

3 

55 

0 

5-25 

6.55 

0.9989 

0.58 

0  73 

0.9949 

2 

89 

3 

62 

0.9909 

5  31 

6  63 

8 

0.63 

0.79 

8 

2 

94 

3 

69 

8 

5-37 

6.71 

7 

0.68 

0.86 

7 

3 

00 

3 

76 

7 

5-44 

6.78 

6 

0.74 

0-93 

6 

3 

06 

3 

83 

6 

5-50 

6.86 

5 

0.79 

0.99 

5 

3 

12 

3 

90 

5 

5  0-6 

6.94 

4 

0.84 

1 .06 

4 

3 

18 

3 

98 

4 

5.62 

7.01 

3 

0.89 

113 

3 

3 

24 

4 

05 

3 

569 

7.09 

2 

0-95 

1. 19 

2 

3 

29 

4 

12 

2 

5-75 

7.17 

1 

1 .00 

1 .26 

I 

3 

35 

4 

20 

I 

5-8i 

7-25 

0 

1 .06 

1-34 

0 

3 

41 

4 

27 

0 

587 

732 

0.9979 

1. 12 

1.42 

0  9939 

3 

47 

4 

34 

0.9899 

5  94 

7  40 

8 

1. 19 

1.49 

8 

3 

53 

4 

42 

8 

6.00 

7.48 

7 

I   25 

1-57 

7 

3 

59 

4 

49 

7 

6.07 

7-57 

6 

I-3I 

1.65 

6 

3 

65 

4 

56 

6 

6.14 

7.66 

S 

1-37 

1-73 

5 

3 

71 

4 

63 

5 

6.21 

7-74 

4 

1.44 

1. 81 

4 

3 

76 

4 

71 

4 

6.28 

7.83 

3 

I   SO 

1.88 

3 

3 

82 

4 

78 

3 

6.36 

7.92 

2 

1.56 

1.96 

2 

3 

88 

4 

85 

2 

6.43 

8.01 

I 

1 .62 

2.04 

I 

3 

94 

4 

93 

I 

6.50 

8.10 

0 

1 .69 

2.12 

0 

4 

00 

S 

00 

0 

6.57 

8.18 

0.9969 

I  75 

2  20 

0.9929 

4 

06 

5 

08 

0.9889 

6  64 

827 

8 

1. 81 

2.27 

8 

4 

12 

5 

16 

8 

6.71 

8.s6 

7 

1.87 

2-35 

7 

4 

19 

5 

24 

7 

6.78 

8.45 

6 

1.94 

2-43 

6 

4 

25 

5 

32 

6 

6.86 

8.54 

5 

2.00 

2-51 

5 

4 

31 

5 

39 

5 

6.93 

8.63 

4 

2.06 

2.58 

4 

4 

37 

5 

47 

4 

7.00 

8.72 

,       3 

2. II 

2.62 

3 

4 

44 

5 

55 

3 

7.07 

8.80 

2 

2.17 

2.72 

2 

4 

50 

5 

63 

2 

7.13 

8.88 

I 

2.22 

2.79 

I 

4 

56 

5 

71 

I 

7.20 

8.96 

0 

2.28 

2.86 

0 

4 

62 

5 

78 

0 

7.27 

9.04 

2l8 


AIR,  WATER,  AND   FOOD 


TABLE  X.  —  {Continued) 

PERCENTAGE  OF  ALCOHOL 


Per  cent 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

Sp.gr. 

ailcohol 

alcohol 

Sp.gr. 

alcohol 

alcohol 

1  Sp.  gr. 

alcohol 

alcohol 

15°.5  C. 

by 

by 

I5°.S  C. 

by 

by 

I5°.S  C. 

by 

by 

weight. 

volume. 

weight. 

volume. 

weight. 

volume. 

0.9879 

7  33 

9  13 

5 

10.46 

12.96 

., 

13-77 

16.98 

8 

7 

40 

9.21 

4 

10.54 

13 

-05 

I 

13 

85 

17 

08 

7 

7 

47 

9.29 

3 

10.62 

13 

15 

0 

13 

92 

17 

17 

6 

7 

53 

9-37 

2 

10.69 

13 

24 

5 

7 

60 

9-45 

I 

10.77 

13 

34 

0.9789 

14 

00 

17 

26 

4 

7 

67 

9-54 

0 

10.85 

13 

43 

8 

14 

09 

17 

37 

3 

7 

73 

9.62 

7 

14 

18 

17 

48 

2 

7 

80 

9.70 

0.9829 

10.92 

13 

52 

6 

14 

27 

17 

59 

I 

7 

87 

9.78 

8 

II  .00 

13 

62 

5 

14 

36 

17 

70 

0 

7 

93 

9.86 

7 

11.08 

13 

72 

4 

14 

45 

17 

81 

6 

II. 15 

13 

81 

3 

14 

55 

17 

92 

0.9869 

8 

00 

9  95 

5 

11.23 

13 

90 

2 

14 

64 

18 

03 

8 

8 

07 

10.03 

4 

II. 31 

13 

99 

I 

14 

73 

18 

14 

7 

8 

14 

10.12 

3 

11.38 

14 

09 

0 

14 

82 

18 

25 

6 

8 

21 

10.21 

2 

11.46 

14 

18 

5 

8 

29 

10.30 

I 

11-54 

14 

27 

0.9779 

14 

90 

18 

36 

4 

8 

36 

10.38 

0 

II  .62 

14 

37 

8 

IS 

00 

18 

48 

3 

8 

43 

10.47 

7 

15 

08 

18 

58 

2 

8 

50 

10.56 

0.9819 

11.69 

14 

46 

6 

15 

17 

18 

68 

I 

8 

57 

10.65 

8 

11.77 

14 

56 

5 

15 

25 

18 

78 

0 

8 

64 

10 -73 

7 

11.85 

14 

65 

4 

15 

2,2, 

18 

88 

0.9859 

8 

71 

10.82 

6 

II  .92 

14 

74 

3 

15 

42 

18 

98 

8 

7 

8 
8 

79 
86 

10.91 
II  .00 

5 
4 

12.00 
12.08 

14 
14 

84 
93 

2 
I 

15 
15 

50 

58 

19 
19 

08 
18 

6 

8 

93 

11.08 

3 
2 

12.15 
12.23 

15 
15 

02 
12 

0 

15 

67 

19 

28 

5 
4 
3 
2 
I 
0 

9 
9 
9 
9 
9 
9 

00 
07 

14 
21 
29 
36 

II. 17 
11.26 

11-35 
11.44 
11.52 
11 .61 

I 
0 

0  9809 

8 
7 

12.31 
12.38 

12.46 

12.54 
12.62 

15 
15 

15 

15 
15 

21 
30 

40 

49 
58 

0.9769 

8 

7 
6 

5 
4 

15 

15 
15 
16 
16 
16 

75 

83 
92 
00 
08 
15 

19 

19 
19 
19 
19 
19 

39 

49 
59 
68 
78 

87 

0.9849 

9 

43 

II  70 

6 

12.69 

15 

68 

3 

16 

23 

19 

96 

8 

9 

50 

11.79 

5 

12.77 

15 

77 

2 

16 

31 

20 

06 

7 

9 

57 

11.87 

4 

12.85 

15 

86 

I 

16 

38 

20 

IS 

6 

9 

64 

11.96 

3 

12.92 

15 

96 

0 

16 

46 

20 

24 

5 

9 

71 

12.05 

2 

13.00 

16 

05 

4 

9 

79 

12.13 

I 

13.08 

16 

15 

0-9759 

16 

54 

20 

33 

3 

9 

86 

12.22 

0 

13-15 

16 

24 

8 

16 

62 

20 

43 

2 

9 

93 

12.31 

7 

16 

69 

20 

52 

I 

10 

00 

12.40 

0.9799 

13  23 

16 

33 

6 

16. 

77 

20 

61 

0 

10 

08 

12.49 

8 

13-31 

16 

43 

5 

16 

85 

20 

71 

7 

13-38 

16 

52 

4 

16 

92 

20 

80 

0.9839 

10 

15 

12.58 

6 

13-46 

16 

61 

3 

17 

00 

20 

89 

8 

10 

23 

12.68 

5 

13-54 

16 

70 

2 

17 

08 

20 

99 

7 

10 

31 

12.77 

4 

13.62 

16 

80 

I 

17 

17 

21 

09 

6 

10 

38 

12.87 

3 

13.69 

16 

89 

0 

17 

25 

21 

19 

APPENDIX  A 


219 


TABLE   X.  —  {Continued) 

PERCENTAGE  OF  ALCOHOL 


Per  cent 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

Sp.gr. 

alcohol 

alcohol 

Sp.  gr. 

alcohol 

alcohol 

Sp.  gr. 

alcohol 

alcohol 

IS°.S  c. 

by 

by 

IS°.5  C. 

by 

by 

I5°.5C. 

by 

by 

weight. 

volume. 

weight. 

volume. 

weight. 

volume. 

0.9749 

17  33 

21.29 

6 

20.00 

24.48 

3 

22.62 

27 -59 

8 

17 

42 

20.39 

5 

20.08 

24 

58 

2 

22 

69 

27 

68 

7 

17 

50 

21.49 

4 

20.17 

24 

68 

I 

22 

77 

27 

77 

6 

17 

58 

21-59 

3 

20.25 

24 

78 

0 

22 

85 

27 

86 

5 

17 

67 

21.69 

2 

20.33 

24 

88 

4 

17 

75 

21.79 

1 

20.42 

24 

98 

0.9679 

22 

92 

27 

95 

3 

17 

83 

21.89 

0 

20.50 

25 

07 

8 

23 

00 

28 

04 

2 

17 

92 

21.99 

7 

23, 

08 

28 

13 

I 

18 

00 

22.09 

0.9709 

20.58 

25 

17 

6 

23 

IS 

28 

22 

0 

18 

08 

22.18 

8 

20.67 

25 

27 

5 

23 

23 

28 

31 

7 

20.75 

25 

37 

4 

23 

31 

28 

41 

0.9739 

18 

15 

22.27 

6 

20.83 

25 

47 

3 

23 

38 

28 

SO 

8 

18 

23 

22.36 

5 

20.92 

25 

57 

2 

23 

46 

28 

59 

7 

18 

31 

22.46 

4 

21.00 

25 

67 

I 

23 

54 

28 

68 

6 

18 

38 

22.55 

3 

21.08 

25 

76 

0 

23 

62 

28 

77 

5 

18 

46 

22.64 

2 

21.15 

25 

86 

4 

18 

54 

22.73 

I 

21  .23 

25 

95 

0.9669 

23 

69 

28 

86 

3 

18 

62 

22.82 

0 

21.31 

26 

04 

8 

23 

77 

28 

95 

2 

18 

69 

22.92 

7 

23 

85 

29 

04 

I 

18 

77 

23.01 

0  9699 

21.38 

26 

13 

6 

23 

92 

29 

13 

0 

18 

85 

23 .  10 

8 

21  .46 

26 

22 

5 

24 

00 

29 

22 

7 

21.54 

26 

31 

4 

24 

08 

29 

31 

0.9729 

18 

92 

23.19 

6 

21  .62 

26 

40 

3 

24 

IS 

29 

40 

8 

19 

00 

23.28 

5 

21.69 

26 

49 

2 

24 

23 

29 

49 

7 

19 

08 

23  38 

4 

21.77 

26 

58 

I 

24 

31 

29 

58 

6 

19 

17 

23  48 

3 

21.85 

26 

67 

0 

24 

38 

29 

67 

5 

19 

25 

23  58 

2 

21  .92 

26 

77 

4 

19 

33 

23.68 

I 

22  .00 

26 

86 

0.9659 

24 

46 

29 

76 

3 

19 

42 

23.78 

0 

22.08 

26 

95 

8 

24 

54 

29 

86 

2 

19 

50 

23.88 

7 

24 

62 

29 

95 

I 

19 

58 

23.98 

0.9689 

22.15 

27 

04 

6 

24 

69 

30 

04 

0 

19 

67 

24.08 

8 

22.23 

27 

13 

5 

24 

77 

30 

13 

7 

22.31 

27 

22 

4 

24 

8S 

30 

22 

0.9719 

19 

75 

24.18 

6 

22.38 

27 

31 

3 

24 

92 

30 

31 

8 

19 

83 

24.28 

5 

22.46 

27 

40 

2 

25 

00 

30 

40 

7 

19 

92 

24  38 

4 

22.54 

27 

49 

220 


AIR,  WATER,  AND   FOOD 


TABLE  XI 


EXTRACT   IN   WINE 

Per  cent  by  Weight 
(According  to  Windisch) 


Sp.gr. 

Ex- 

Sp. gr. 

Ex- 

Sp. gr. 

Ex- 

Sp.gr. 

Ex- 

Sp.gr. 

E.X- 

Sp.  gr. 

Ex- 

tract. 

tract. 

tract. 

tract. 

tract. 

tract. 

I.OOOO 

0.00 

1.0200 

5.17 

I . 0400 

10.35 

I . 0600 

IS.  55 

I . 0800 

20.78 

I. 1000 

26.04 

I.  coos 

0.13 

1. 0205 

5. 30 

I. 040s 

10.48 

I. 060s 

15.68 

1.0805 

20.91 

I. 1005 

26.17 

1. 0010 

0.26 

I. 0210 

S.43 

I. 0410 

10.61 

I. 0610 

15.81 

I. 0810 

21.04 

I.IOIO 

26.30 

l.oois 

0.39 

I. 0215 

5.56 

1.041S 

10.74 

I. 0615 

15.94 

I. 0815 

21.17 

1.1015 

26.43 

I.O020 

0.52 

I . 0220 

5.69 

1.0420 

10.87 

I . 0620 

16.07 

1.0820 

21.31 

I . 1020 

26.56 

I.002S 

0.64 

1. 0225 

5.82 

1.042s 

11.00 

1.062s 

16. 21 

1.082s 

21.44 

I . 1025 

26.70 

1.0030 

0.77 

1.0230 

5. 94 

1.0430 

II.  13 

1.0630 

16.33 

1.0830 

21.57 

I . 1030 

26.83 

1.003s 

0.90 

1.023s 

6.07 

I. 0435 

11.26 

1.0635 

16.47 

1.0835 

21.70 

I . 103s 

26.96 

I . 0040 

1.03 

1.0240 

6.20 

I . 0440 

11.39 

I . 0640 

16.60 

1.0840 

21.83 

I . 1040 

27.09 

1.0045 

1. 16 

1.0245 

6.33 

1.0445 

11.52 

1.0645 

16.73 

1.084s 

21.96 

I. 1045 

27.22 

I . 0050 

1.29 

1.0250 

6:46 

1.0450 

11.65 

1.0650 

16.86 

1.0850 

22.09 

I . 1050 

27.3s 

1.005s 

1.42 

I. 0255 

6.59 

1.045s 

11.78 

1.0655 

16.99 

1.0855 

22.22 

I. 1055 

27.49 

1.0060 

i.SS 

I . 0260 

6.72 

1.0460 

11.91 

I . 0660 

17.12 

1.0860 

22.36 

I. 1060 

27.62 

1.0065 

1.68 

1.026s 

6.85 

1.046s 

12.04 

1.0665 

17.2s 

1.0865 

22.49 

I . 1065 

27. 75 

1.0070 

1. 81 

1.0270 

'6.98 

1.0470 

12.17 

I . 0670 

17.38 

1.0870 

22.62 

I . 1070 

27.88 

1.0075 

I  94 

1.027s 

7:11 

1.0475 

12.30 

1.0675 

17.51 

1.087s 

22.75 

I. 1075 

28.01 

1.0080 

2.07 

1.0280 

7*24 

I . 0480 

12.43 

1.0680 

17.64 

1.0880 

22.88 

I . 1080 

28.15 

1.008s 

2.19 

I . 0285 

J -37 

1.048s 

12.56 

1.0685 

17.77 

1.088s 

23.01 

I . 1085 

28.28 

1.0090 

2.32 

I . 0290 

Vso 

I . 0490 

12.69 

I . 0690 

17.90 

1.0890 

23.14 

I. 1090 

28.41 

1.009s 

2.4s 

1.029s 

7.63 

1.0495 

12.82 

1.069s 

18.03 

1.089s 

23.28 

I. 1095 

28.54 

I. 0100 

2.S8 

I . 0300 

7.76 

i.osoo 

12.95 

1.0700 

18.16 

1.0900 

23.41 

I.IIOO 

28.67 

i.oios 

2.71 

1.030s 

7.89 

i.osos 

13.08 

I. 070s 

18.30 

1.0905 

23.54 

i.iios 

28.81 

I. Olio 

2.84 

I. 0310 

8.02 

1.0510 

13-21 

I. 0710 

18.43 

I. 0910 

23.67 

I. mo 

28.94 

ions 

2.97 

I. 0315 

8.14 

1.0515 

13.34 

I. 0715 

18.  s6 

1.0915 

23.80 

1.1115 

29.07 

1. 0120 

3  10 

1.0320 

8.27 

1.0520 

13.47 

1.0720 

18.69 

1.0920 

23.93 

1.1120 

29.20 

I. 0125 

3.23 

1.032s 

8.40 

1.0525 

13.60 

1.0725 

18.82 

1.092s 

24.07 

1.1125 

29.33 

I. 0130 

3.36 

1.0330 

8.53 

I . 0530 

13.73 

1.0730 

18.95 

1.0930 

24.20 

1.1130 

29.47 

I. 0135 

3.49 

I. 0335 

8.66 

1.0535 

13.86 

1.0735 

19.08 

1.0935 

24.33 

I.II3S 

29.60 

I. 0140 

3.62 

1.0340 

8.79 

I . 0540 

13  99 

1.0740 

19.21 

1.0940 

24.46 

1.1140 

29.73 

1.014s 

3.7s 

1.0,345 

8.92 

I. 0545 

14.12 

1.0745 

19.34 

I. 0945 

24. 59 

1.1145 

29.86 

I. 0150 

3.87 

1.0350 

9.05 

I. 0550 

14.25 

1.0750 

19.47 

1.0950 

24.72 

i.iiso 

29.99 

I. 015s 

4.00 

1.0355 

9.18 

I.0SS5 

14.38 

1.0755 

19.60 

1 . 0955 

24.85 

l.iiSS 

30.13 

I. 0160 

4.13 

1.0360 

9-31 

1.0560 

14. SI 

1 . 0760 

19.73 

1.0960 

24.99 

1.016s 

4.26 

1.0365 

9.44 

1.0565 

14.64 

1.0765 

19.86 

1.0965 

25.12 

I. 0170 

4.39 

1.0370 

9.57 

1.0570 

14.77 

1.0770 

20.00 

1.0970 

25.25 

I.0I7S 

4.52 

I  0375 

9  70 

I. 057s 

14.90 

1.077s 

20.12 

1.097s 

25.38 

I. 0180 

4.6s 

I . 0380 

9.83 

1.0580 

15.03 

1.0780 

20.26 

1.0980 

25.51 

I. 0185 

4.78 

1.038s 

9.96 

1.0585 

15.16 

1.0785 

20.39 

1.098s 

25.64 

I. 0190 

4.91 

1.0390 

10.09 

1.0590 

15.29 

1.0790 

20.52 

1 . 0990 

25.78 

I  0195 

S.04 

1.0395 

10.22 

1.0595 

15.42 

1.0795 

20.65 

1.0995 

25.91 

APPENDIX  A 


221 


TABLE   XII 


TABLE   FOR    REDUCING   SUGAR  CONDENSED   FROM   THAT  OF 
MUNSON  AND    WALKER 

(Expressed  in  milligrams) 


oj 

d 

6 

d 

12 

Is 

6 

2 

a 
3 

■  X 

0+ 

H 

§0 

0 
1 

n! 

3 

it 

sQ. 

3  3 

SO 

Q 

^i 

So 

u ' — 

0. 

3 

a 

l| 

"5= 

O 

0 

0 

J 

10 

4.0 

4-5 

4.0 

5.9 

260 

117.6 

121.4 

178.3 

203.9 

IS 

6.2 

6.7 

75 

9  9 

265 

120.0 

123.9 

181. 9 

207.9 

20 

8.3 

8.9 

10  9 

13.8 

270 

122.5 

126.4 

185-4 

211. & 

25 

10.5 

II. 2 

14-4 

17.8 

275 

124.9 

128.9 

188.9 

215. & 

30 

12,6 

13.4 

17.8 

21.8 

280 

127.3 

131. 4 

192.4 

219.7 

35 

14.8 

15.6 

21.3 

25.7 

285 

129.8 

133  9 

196.0 

223.7 

40 

16.9 

17.8 

24.8 

29.7 

290 

132.3 

136.4 

199  5 

227.6 

45 

19. 1 

20.1 

28.2 

33.7 

295 

134.7 

138.9 

203.0 

231.6 

50 

21.3 

22.3 

31-7 

37.6 

300 

137.2 

141.5 

206  6 

235. 5 

SS 

23.5 

24.6 

35  I 

41.6 

305 

139.7 

144.0 

210. 1 

239.  S 

6o 

25.6 

26.8 

38.6 

45-6 

310 

142.2 

146.6 

213.7 

243.5 

65 

27.8 

29.1 

42.1 

49-5 

315 

144.7 

149  1 

217.2 

247-4 

70 

30.0 

31-3 

45  5 

53-5 

320 

147-2 

15I-7 

220.7 

251-3 

75 

32.2 

33-6 

49.0 

57-5 

325 

149-7 

154-3 

224-3 

255-3 

8o 

34-4 

35-9 

52.5 

61.4 

330 

152.2 

156.8 

227.8 

259-3 

85 

36.7 

38.2 

56.0 

65.4 

335 

154.7 

159-4 

231.4 

263.2 

90 

38.9 

40.4 

59-4 

69.3 

340 

157-3 

162.0 

234.9 

267.1 

95 

41. 1 

42.7 

62  9 

73-3 

345 

159  8 

164.6 

238.5 

271. 1 

100 

43-3 

450 

66.4 

77.3 

350 

162.4 

167.2 

242  0 

275.0 

105 

45.5 

47-3 

69.8 

81.2 

355 

164.9 

169.8 

245-6 

279.0 

no 

47.8 

49.6 

73.3 

85.2 

360 

167-5 

172  5 

249 -1 

282.9 

115 

50.0 

51.9 

76.8 

89.2 

365 

170. 1 

175- 1 

252-7 

286.9 

120 

52.3 

54.3 

80.3 

93  I 

370 

172-7 

177  7 

256.2 

290.8 

125 

54-5 

56.6 

83.8 

97.1 

375 

175-3 

180 -4 

2.S9-8 

294.8 

130 

56.8 

58.9 

87.3 

lOI.O 

380 

177-9 

183.0 

263-4 

298.7 

13s 

59.0 

61.2 

90.8 

105.0 

385 

180.5 

18s.  7 

266.9 

302.7 

140 

61.3 

63.6 

94.2 

109.0 

390 

183.1 

188.4 

270.5 

306.6 

145 

63.6 

65.9 

97.7 

112. 9 

395 

185.7 

191  0 

274-0 

310.6 

150 

659 

68.3 

IOI.2 

116. 9 

400 

188  4 

193-7 

277-6 

314.5 

ISS 

68.2 

70.6 

104.7 

120.8 

405 

191. 0 

196.4 

281.1 

318.5 

160 

70.4 

73.0 

108.2 

124.8 

410 

193.7 

199.1 

284.7 

322.4 

16S 

72.8 

75.3 

III. 7 

128.8 

415 

196.3 

201.8 

288.3 

326.3 

170 

75.1 

77.7 

115. 2 

132.7 

420 

199  0 

204.6 

291.9 

3.30.3 

175 

77.4 

80.1 

118. 7 

136.7 

425 

201.7 

207.3 

295-4 

334-2 

180 

79.7 

82.5 

122.2 

140.6 

430 

204.4 

210.0 

299.0 

338.2 

185 

84.2 

84.9 

125.7 

144.6 

435 

207.1 

212.8 

302.6 

342.1 

190 

84.3 

87.2 

129.2 

148.6 

440 

209.8 

215.5 

306.2 

346.1 

195 

86.7 

89.6 

132.7 

152. 5 

445 

212.5 

218.3 

309.7 

350.0 

200 

89.0 

92.0 

136.2 

156.5 

450 

215.2 

221.1 

313  3 

353. 9 

205 

91.4 

94.5 

139.7 

160.4 

455 

218.0 

223.9 

316.9 

357  9 

210 

93.7 

96  9 

143  2 

164.4 

460 

220.7 

226.7 

320. 5 

361.8 

215 

96.1 

99-3 

146  7 

168.3 

46s 

223. 5 

229.5 

324.1 

365.8 

220 

98.4 

IOI.7 

150.2 

172.3 

470 

226.2 

232.3 

327.7 

369.7 

225 

100.8 

104.2 

153-7 

176.2 

475 

229.0 

235.1 

331.3 

3-3.7 

230 

103.2 

106.6 

157.2 

180.2 

480 

231.8 

237-9 

334.8 

377.6 

235 

105.6 

109. 1 

160.7 

184.2 

485 

234.6 

240.8 

338.4 

381.5 

240 

108.0 

III. 5 

164.3 

188.1 

490 

237.4 

243.6 

342.0 

385.5 

245 

no. 4 

114  0 

167.8 

192. 1 

250 

112. 8 

116  4 

171. 3 

196.0 

255 

IIS-2 

118. 9 

174.8 

200.0 

222 


AIR,   WATER,   AND   FOOD 


TABLE  XIII 


EXTRACT  IN   BEER-WORT 

(According  to  Schultz  and  Ostermann) 


Specific 

Extract. 

Specific 

Extract. 

Specific 

Extract.         Sp 

ecific 

Extract. 

gravity  at 

Per  cent 

gravity  at 

Per  cent 

gravity  at 

Per  cent       gra 

i/ity  at 

Per  cent 

IS°C. 

by  weight. 

15°  c. 

by  weight. 

15°  c. 

by  weight.         i. 

°C. 

jy  weight. 

I .0000 

0.00 

I .0235 

6.07 

I .0470 

11.89           I. 

0705 

17.59 

I  .  0005 

013 

1.0240 

6. 19 

1.0475 

12.01           I. 

0710 

17.70 

I .0010 

0.26 

1.0245 

6.31 

I . 0480 

12.14           I 

0715 

17.81 

1. 0015 

0.39 

I .0250 

6.44 

1.0485 

12.26           I 

0720 

17  93 

1.0020 

0.52 

I .0255 

6.58 

I . 0490 

12.38           I 

0725 

18.04 

1.0025 

0.66 

I .0260 

6.71 

I    0495 

I  2 . 50             I 

0730 

18.15 

1.0030 

0.79 

1.0265 

6.85 

I .0500 

12.63             I 

0735 

18.26 

I  0035 

0.92 

I .0270 

6.99 

1-0505 

12.75             I 

0740 

18.38 

1.0040 

I -OS 

1.0275 

7.12 

I. 0510 

12.87             I 

0745 

18.49 

1.004s 

1. 18 

1.0280 

7.26 

I    0515 

12.99             I 

0750 

18.59 

1.0050 

1.31 

1.0285 

7.37 

I .0520 

13.12             I 

0755 

1S.70 

I  0055 

1.44 

1.0290 

7.48 

1-0525 

13.24             I 

0760 

18.81 

I . 0060 

1.56 

1.0295 

7.60 

1-0530 

13.36             I 

0765 

18.91 

1.0065 

1.69 

I . 0300 

7.71 

1-0535 

13.48             I 

0770 

19.02 

1.0070 

1.82 

1.0305 

7.82 

1.0540 

13.61             I 

0775, 

19.12 

1.0075 

1-95 

I. 0310 

7-93 

I -054s 

13-73         I 

0780 

19.23 

I .0080 

2.07 

1-0315 

8.04 

I    0550 

13.86         I 

0785 

1933 

I . 0085 

2.20 

1.0320 

8.16 

1.0555 

13.98         I 

0790 

19.44 

I . 0090 

2.33 

I   0325 

8.27 

I . 0560 

H-ii         I 

0795 

19.56 

I .0095 

2.46 

1.0330 

8.40 

1-0565 

14.23         I 

0800 

19.67 

I .0100 

2.58 

1-0335 

8.53 

1.0570 

14.36         I 

0805 

19.79 

I. 0105 

2.71 

1.0340 

8.67 

1-0575 

14.49         I 

0810 

19.91 

I .0110 

2.84 

I -0345 

8.80 

1.0580 

14.62         I 

0815 

20.03 

I.0115 

2.97 

1.0350 

8.94 

1.0585 

14-75         I 

0820 

20. 14 

I. 01 20 

3.10 

I -0355 

9.07 

1.0590 

14.89         I 

0825 

20.  26 

I. 0125 

3  23 

1.0360 

9.21 

1.0595 

15.02         I 

0830 

20.37 

I. 0130 

3-35 

I  0365 

9.34 

I .0600 

15-14         I 

0835 

20.48 

I .0135 

3-48 

1.0370 

9-45 

I .0605 

15-25         I 

0840 

20.59 

I .0140 

3.61 

I -037s 

9-57 

I .0610 

15.36         I 

0845 

20.70 

I. 0145 

3.74 

I .0380 

9.69 

I . 06 1 5 

1547         I 

0850 

20,81 

1. 0150 

387 

1-0385 

9.81 

I .0620 

15-58         I 

0855 

20.93 

1.015s 

4.00 

1.0390 

9.92 

I .0625 

15.69         I 

0860 

21.06 

I .0160 

4.13 

1.0395 

10.04 

I . 0630 

15.80         I 

0865 

21 .19 

I. 0165 

4.26 

I . 0400 

10.16 

1.0635 

15.92         I 

0870 

21-33 

I. 01 70 

4-39 

I . 0405 

10.27 

I . 0640 

16.03         I 

0875 

21-43 

I. 0175 

4-53 

I .0410 

10.40 

1.0645 

16.14         I 

0880 

21-54 

I .0180 

4.66 

I. 0415 

10.52 

I .0650 

16.25         I 

0885 

21.64 

I. 0185 

4-79 

I .0420 

10.65 

1.0655 

16.37         I 

0890 

21-75 

I .0190 

4.93 

1.0425 

10. -7 

I . 0660 

16.50         I 

0895 

21.86 

I. 0195 

5.06 

1.0430 

10.90 

I .0665 

16.62         I 

.0900 

21.98 

I .0200 

5.20 

1.0435 

11.03 

I .0670 

16.74         I 

.0905 

22.08 

1.0205 

5-33 

1 .0440 

II. 15 

1.0675 

16.86         I 

.0910 

22. 19 

I .0210 

5-45 

I .0445 

11.28 

I . 0680 

16.99         I 

•0915 

22.30 

I. 0215 

5-57 

1.0450 

II  .40 

1.0685 

17. II         I 

.0920 

22.41 

I .0220 

5 -70 

1-0455 

11.53 

I . 0690 

17.23         I 

•0925 

22.52 

I .0225 

5-82 

I . 0460 

11.65 

I .0695 

17.35         I 

.0930 

22.63 

1.0230 

5-94 

1.0465 

11.77 

I .0700 

17.48         I 

.0935 

22.73 

APPENDIX  A 


223 


TABLE   XIII.  —  {Continued} 

EXTRACT   IN   BEER-WORT 

(According  to  Schultz  and  Ostermann) 


Specific 

Extract. 

Specific 

Extract. 

Specific 

Extract. 

Specific 

Extract. 

gravity  at 

Per  cent 

gravity  at 

Per  cent 

gravity  at 

Per  cent 

gravity  at 

Per  cent 

15°  c. 

by  weight. 

15°  c. 

by  weight. 

15°  C. 

by  weight. 

15°  c. 

by  weight. 

1.0940 

22.84 

1 . 1020 

24-53 

I .1100 

26.27 

I.I180 

27.88 

0945 

22.94 

1. 1025 

24.64 

I. I 105 

26.37 

1.118s 

27.98 

0950 

23   05 

I . 1030 

24-74 

I  .1110 

26.48 

1.1190 

28.09 

095s 

23.16 

I -1035 

24.85 

I.III5 

26.58 

1.1195 

28.19 

0960 

23.27 

I . 1040 

24.96 

I.II20 

26.68 

1.1200 

28.28 

0965 

2337 

I . 1045 

25-07 

I .1125 

26.79 

1 . 1 205 

28.38 

0970 

23-48 

I. 1050 

25  .  18 

I. 1 130 

26.89 

I .1210 

28.48 

0975 

23 -59 

I    1055 

25.29 

I-II35 

26.99 

1.1215 

28.58 

0980 

23.69 

I . 1060 

25-40 

I.II40 

27.09 

1 .1220 

28.68 

0985 

23.80 

1-1065 

25-50 

I-II45 

27.19 

1 .1225 

28.78 

0990 

23.90 

I . 1070 

25.61 

I . II50 

27.29 

1.1230 

28.88 

0995 

24.01 

1.107s 

25-71 

I-II55 

27.38 

I-I235 

28.98 

1000 

24.  II 

I . 1080 

25-82 

I . I160 

27.48 

1.1240 

29.08 

1005 

24.21 

1-1085 

25-93 

I.I165 

27-58 

I -1245 

29.18 

1010 

24.32 

I . 1090 

26.05 

I .1170 

27.68 

1.1250 

29.28 

1015 

24 -43 

I. 1095 

26.  16 

I-II75 

27-78 

I-I255 

29.38 

224 


AIR,  WATER,  AND   FOOD 


LOGARITHMS 

OF 

NUMBERS 

Natural 

Proportional  parts. 

num- 

0 

I 

2 

3 

4 

5 

6 

7 

8 

9 

bers. 

I 
4 

2 
8 

3 

12 

4 

17 

5 
21 

6 

25 

7 

29 

8 

33 

0 

lO 

0000 

0043 

0086 

0128 

0170 

0212 

0253 

0294 

0334 

0374 

37 

II 

0414  0453 '040 2 

0531 

0569 

0607 

0645 

0682 

0719 

0755 

4 

8 

II 

15 

19 

23 

26 

30 

34 

12 

0792  0828,0864 

0899 

0934 

0969 

1004 

1038 

1072 

1 106 

3 

7 

10 

14 

17 

21 

24 

28 

31 

13 

1139 

1173 

1206 

1239 

1271 

1303 

1335 

1367 

1399 

1430 

3 

6 

10 

13 

16 

19 

23 

26 

29 

14 

1461 

1492 

1523 

1553 

1584 

1614 

1644 

1673 

1703 

1732 

3 

6 

9 

12 

IS 

18 

21 

24 

27 

IS 

1761 

1790 

1818 

1847 

1875 

1903 

1931 

1959 

1987 

2014 

3 

6 

8 

II 

14 

17 

20 

22 

25 

16 

2041 

2068 

209s 

2122 

2148 

2175 

2201 

2227 

2253 

2279 

3 

5 

8 

II 

13 

16 

18 

21 

24 

17 

2304 

2330 

2355 

2380 

2405 

2430 

2455 

2480 

2504 

2529 

2 

5 

7 

10 

12 

15 

17 

20 

22 

18 

2553 

2577 

2601 

2625 

2648 

2672 

2695 

2718 

2742 

2765 

2 

S 

7 

9 

12 

14 

16 

19 

21 

19 

2788 

2810 

2833 

2856 

2878 

2900 

2923 

294s 

2967 

2989 

2 

4 

7 

9 

II 

13 

16 

18 

20 

20 

3010 

3032 

3054 

3075 

3096 

3118 

3139 

3160 

3181 

3201 

2 

4 

6 

8 

II 

13 

15 

17 

19 

21 

3222 

3243 

3263 

3284 

3304 

3324 

3345 

3365 

3385 

3404 

2 

4 

6 

8 

10 

12 

14 

16 

18 

22 

3424 

3444 

3464 

3483 

3502 

3522 

3541 

3560 

3579 

3598 

2 

4 

6 

8 

10 

12 

14 

15 

17 

23 

3617 

3636 

3655 

3674 

3692 

3711 

3729 

3747 

3766 

3784 

2 

4 

6 

7 

9 

II 

13 

15 

17 

24 

3802 

3820 

3838 

3856 

3874 

3892 

3909 

3927 

3945 

3962 

2 

4 

5 

7 

9 

II 

12 

14 

16 

25 

3979 

3997 

4014 

4031 

4048 

4065 

4082 

4099 

4116 

4133 

2 

3 

5 

7 

9 

10 

12 

14 

IS 

26 

4150 

4166 

4183 

4200 

4216 

4232 

4249 

4265 

4281 

4298 

2 

3 

5 

7 

8 

10 

II 

13 

IS 

27 

4314 

4330 

4346 

4362 

4378 

4393 

4409 

4425 

4440 

4456 

2 

3 

S 

6 

8 

9 

II 

13 

14 

28 

4472 

4487 

4502 

4518 

4533 

4548 

4564 

4579 

4594 

4609 

2 

3 

5 

6 

8 

9 

II 

12 

14 

29 

4624 

4639 

4654 

4669 

4683 

4698 

4713 

4728 

4742 

4757 

I 

3 

4 

6 

7 

9 

10 

12 

13 

30 

4771 

4786 

4800 

4814 

4829 

4843 

4857 

4871 

4886 

4900 

3 

4 

6 

7 

9 

10 

II 

13 

31 

4914 

4928 

4942 

4955 

4969 

4983 

4997 

501 1 

5024 

5038 

3 

4 

6 

7 

8 

10 

11 

12 

32 

5051 

5065 

5079 

5092 

5105 

5119 

5132 

5145 

5159 

5172 

3 

4 

5 

7 

8 

9 

II 

12 

33 

5185 

S198 

5211 

5224 

5237 

5250 

5263 

5276 

5289 

5302 

3 

4 

5 

6 

8 

9 

10 

12 

34 

5315 

5328 

5340 

5353 

5366 

5378 

5391 

5403 

5416 

5428 

3 

4 

5 

6 

8 

9 

10 

II 

35 

5441 

5453 

5465 

5478 

5490 

5502 

5514 

5527 

5539 

5551 

2 

4 

S 

6 

7 

9 

10 

II 

36 

5563 

5575 

5587 

5599 

5611 

5623 

5635 

5647 

5658 

5670 

2 

4 

5 

6 

7 

8 

10 

II 

37 

5682 

5694 

5705 

5717 

5729 

5740 

5752 

5763 

5775 

5786 

2 

3 

5 

6 

7 

8 

9 

10 

38 

5798 

5S09 

5821 

5832 

5843 

5855 

5866 

5877 

5888 

5899 

2 

3 

5 

6 

7 

8 

9 

10 

39 

59" 

5922 

5933 

5944 

5955 

5966 

5977 

5988 

5999 

6010 

2 

3 

4 

S 

7 

8 

9 

10 

40 

6021 

6031 

6042 

6053 

6064 

6075 

6085 

6096 

6x07 

6117 

2 

3 

4 

5 

6 

8 

9 

10 

41 

6128 

6138 

6149 

6160 

6170 

6180 

6191 

6201 

6212 

6222 

2 

3 

4 

5 

6 

7 

8 

9 

42 

6232 

6243 

6253 

6263 

6274 

62S4 

6294 

6304 

6314 

6325 

2 

3 

4 

5 

6 

7 

8 

9 

43 

6335 

6345 

6355 

6365 

6375 

6385 

6395 

6405 

6415 

6425 

2 

3 

4 

5 

6 

7 

8 

9 

44 

6435 

6444 

6454 

6464 

6474 

6484 

6493 

6503 

6513 

6522 

2 

3 

4 

5 

6 

7 

8 

9 

45 

6532 

6542 

6551 

6561 

6571 

6580 

6590 

6599 

6609 

6618 

2 

3 

4 

S 

6 

7 

8 

9 

46 

6628 

6637 

6646 

6656 

6665 

6675 

6684 

6693 

6702 

6712 

2 

3 

4 

5 

6 

7 

7 

8 

47 

6721 

6730 

6739 

6749 

6758 

6767 

6776 

6785 

6794 

6803 

2 

3 

4 

5 

5 

6 

7 

8 

48 

6812 

6821 

6830 

6839 

6848 

6857 

6866 

6875 

6884 

6893 

2 

3 

4 

4 

5 

6 

7 

8 

49 

6902 

69 1 1 

6920 

6928 

6937 

6946 

6955 

6964 

6972 

6981 

2 

3 

4 

4 

5 

6 

7 

8 

50 

6990 

6998 

7007 

7016 

7024 

7033 

7042 

7050 

7059 

7067 

2 

3 

3 

4 

S 

6 

7 

8 

51 

7076 

7084 

7093 

7101 

7110 

7118 

7126 

7135 

7143 

7152 

2 

3 

3 

4 

S 

6 

7 

8 

52 

7160 

7168 

7177 

7185 

7193 

7202 

7210 

7218 

7226 

7235 

2 

2 

3 

4 

5 

6 

7 

7 

53 

7243 

7251 

7259 

7267 

7275 

7284 

7292 

7300 

7308 

7316 

2 

2 

3 

4 

5 

6 

6 

7 

54 

7324 

7332 

7340 

7348 

7356 

7364 

7372 

7380 

7388 

7396 

2 

2 

3 

4 

5 

6 

6 

7 

APPENDIX   A 


225 


LOGARITHMS 

OF 

NUMBERS 

Natura 

Proport 

onal  parts. 

num- 

0 

I 

7412 

2 
7419 

3 

4 

5 

6 

7 
7459 

8 

9 

bers. 

I  234 

567  8  9 

55 

7404 

7427 

7435 

7443 

7451 

7466 

7474   122, 

(45567 

56 

7482 

7490 

7497 

7505 

7513 

7520 

7528 

7536 

7543 

7551   122. 

(45567 

57 

7559 

7566 

7574 

7582 

7589 

7597 

7604 

7612 

7619 

7627   122, 

145567 

5« 

7634 

7642 

7649 

7657 

7664 

7672 

7679 

7686 

7694 

7701   112: 

44567 

59 

7709 

7716 

7723 

7731 

7738 

7745 

7752 

7760 

7767 

7774   112; 

44567 

60 

7782 

7789 

7796 

7803 

7810 

7818 

7825 

7832 

7839 

7846    I  2  : 

44566 

61 

7853 

7860 

7868 

7875 

7882 

7889 

7896 

7903 

7910 

7917  I  1  2  i 

44566 

62 

7924 

7931 

7938 

7945 

7952 

7959 

7966 

7973 

7980 

7987  I  I  2  2 

34566 

63 

7993 

8000 

8007 

8oi4!8o2i 

8028 

8035 

8041 

8048 

8055  I  I  2  3 

3  4  5  S  6 

64 

8062 

8069 

S075 

8082 

8089 

8096 

8102 

8109 

8116 

8122  I  I  2  3 

3  4  S  S  6 

65 

8129 

8136 

8142 

8149 

8156 

8162 

8169 

8176 

8182 

8189  I  I  2  3 

34556 

66 

S195 

8202 

8209 

8215 

8222 

8228 

8235 

8241 

8248 

8254  I  I  2  3 

3  4  5  5  6 

67 

8261 

8267 

8274 

8280 

8287 

8293 

8299 

S306 

8312 

8319  I  I  2  3 

34556 

68 

8325 

8331 

8338 

8344 

8351 

8357 

8363 

8370 

8376 

8382  1123 

34456 

69 

8388 

839s 

8401 

8407 

8414 

8420 

8426 

8432 

8439 

8445  I  I  2  2 

34456 

70 

8451 

8457 

8463 

8470 

8476 

8482 

8488 

8494 

8500 

8506  I  I  2  2 

3  4  4  5  6 

71 

8513 

8519 

8525 

8531 

S537 

8543 

8549 

8555 

S561 

8567  I  I  2  2 

3  4  4  5  5 

72 

8573 

8579 

8585 

8591 

8597 

8603 

S609 

861S 

8621 

8627  I  I  2  2 

3  4  4  5  S 

73 

8633 

S630 

S645 

8651 

8657 

8663 

8669 

8675 

8681 

8686  1122 

3  4  4  5  5 

74 

8692 

8698 

8704 

8710 

8716 

8722 

8727 

S733 

8739 

8745  1122 

3  4  4  5  S 

75 

8751 

8756 

8762 

8768 

8774 

8779 

8785 

8791 

8797 

8802  I  I  2  2 

33455 

76 

8808 

8814 

8820 

8825 

8831 

8837 

8842 

8848 

8854 

8859  I  I  2  2 

3  3  4  5  S 

77 

8865 

8871 

8876 

8SS2 

888  7 

8893 

8899 

S904 

8910 

8915  I  I  2  2 

3  3  4  4  5 

'  78 

8921 

8927 

8932 

S938 

8943 

8949 

8954 

8960 

8965 

8971   I  I  2  2 

3  3  4  4  5 

79 

8976 

8982 

S987 

8993 

8998 

9004 

9009 

9015 

9020 

9026  I  I  2  2 

3  3  4  4  5 

80 

9031 

9036 

9042 

9047 

9053 

9058 

9063 

9069 

9074 

9079  I  I  2  2 

3  3  4  4  5 

81 

9085 

9090 

9096 

9101 

9106 

9112 

9117 

9122 

9128 

9133  1122 

3  3  4  4  5 

82 

9138 

9143 

9149 

9154 

9159 

9165 

9170 

9175 

9180 

9186  I  I  2  2 

3  3  4  4  5 

83 

9191 

9196 

9201 

9206 

9212 

9217 

9222 

9227 

9232 

9238  I  I  2  2 

3  3  4  4  5 

84 

9243 

9248 

9253 

9258 

9263 

9269 

9274 

9279 

9284 

9289  I  I  2  2 

3  3  4  4  S 

85 

9294 

9299 

9304 

9309 

9315 

9320 

9325 

9330 

9335 

9340  I  I  2  2 

3  3  4  4  5 

86 

9345 

9350 

9355 

9360 

9365 

9370 

9375 

9380 

9385 

9390  I  I  2  2 

3  3  4  4  5 

87 

9395 

9400 

9405 

9410 

0415 

9420 

9425 

9430 

0435 

0440  0  I  I  2 

23344 

88 

9445 

9450 

0455 

9460 

0465 

0460 

9474 

9470 

9484 

9489  0  I  I  2 

23344 

89 

9494 

9499 

9504 

9509 

9513 

9518 

9523 

9528 

9533 

9538  0  I  I  2 

2  3  3  4  4 

90 

9542 

9547 

9552 

9557 

9562 

9566 

9571 

9576 

9581 

9586  0  I  I  2 

23344 

91 

9590 

9595 

9600 

9605 

9609 

9614 

9619 

9624 

9628 

9633  0  I  I  2 

23344 

92 

9638 

9643 

9647 

9652 

9657 

9661 

9666 

9671 

9675 

9680  0  I  I  2 

2  3  3  4  4 

93 

9685 

9689 

9694 

9699 

9703 

9708 

9713 

9717 

9722 

9727  0  I  I  2 

2  3  3  4  J 

94 

9731 

9736 

9741 

9745 

9750 

9754 

9759 

9763 

9768 

9773  0  I  I  2 

23344 

95 

9777 

9782 

9786 

9791 

9795 

9800 

9805 

9809 

9814 

9818  0  I  I  2 

23344 

96 

98  23 

9827 

9832 

9836 

9841 

9845 

Q850 

9854 

0S59 

0S63   0  I  I  2 

23344 

97 

9868 

9S72 

9877 

9881 

9886 

98QO 

0804 

0899 

9903 

90o8  0112 

23344 

98 

9912 

9917 

9921 

9926 

9930 

9934 

0939 

9943 

9948 

9Q52   0  I  I  2 

23344 

99   9956 

9961 

9965 

9969 

9974 

9978 

9983  J 

9987 

9991 

9996  0  I  I  2 

23334 

226 


AIR,   WATER,   AND   FOOD 


ANTILOGARITHMS 


Loga- 
rithms. 

0 

I 

2 

3 

4 

5 

6 

7 

8 

9 

Proportional  parts. 

I 

2 
0 

3 

4 

5 

6 

I 

7 

2 

8 

2 

9 

O.OO 

1000 

1002 

1005 

1007 

1009 

1012 

1014 

IO16 

1019 

1021 

0 

2 

O.OI 

1023 

1026  1028 

1030 

1033 

1035 

1038 

1040 

1042 

1045 

0 

0 

I 

2 

2 

2 

0.02 

1047 

1050  1052 

1054 

1057 

1059 

1062 

1064 

1067 

1069 

0 

0 

I 

2 

2 

2 

0.03 

1072 

1074 

1076 

1079 

1081 

1084 

1086 

1089 

1091 

1094 

0 

0 

I 

2 

2 

2 

0.04 

1096 

1099 

1102 

1 104 

II07 

1 109 

1112 

II14 

1117 

III9 

0 

2 

2 

2 

2 

0.05 

II22 

1125 

1127 

1 130 

II32 

"35 

1 138 

1 140 

"43 

1 146 

0 

2 

2 

2 

2 

0.06 

1 148 

1151 

"53 

II56 

"59 

1161 

1 164 

I167 

1 169 

I172 

0 

2 

2 

2 

2 

0.07 

"75 

1178 

iiSo 

1 183 

1186 

1 189 

1191 

"94 

"97 

"99 

0 

2 

2 

2 

2 

0.08 

1202 

1205 

1208 

I2II 

1213 

1216 

1219 

1222 

1225 

1227 

0 

2 

2 

2 

3 

0.09 

1230 

1233 

1236 

1239 

1242 

1245 

1247 

1250 

1253 

1256 

0 

2 

2 

2 

3 

O.IO 

1259 

1262 

1265 

1268 

1271 

1274 

1276 

1279 

1282 

1285 

0 

2 

2 

2 

3 

O.II 

1288 

1291 

1294 

1297 

1300 

1303 

1306 

1309 

1312 

1315 

0 

2 

2 

2 

2 

3 

0.12 

1318 

1321 

1324 

1327 

1330 

1334 

1337 

1340 

1343 

1346 

0 

2 

2 

2 

2 

3 

0.13 

1349 

1352 

1355 

1358 

1361 

1365 

1368 

1371 

1374 

1377 

0 

2 

2 

2 

3 

3 

0. 14 

1380 

1384 

1387 

1390 

1393 

1396 

1400 

1403 

1406 

1409 

0 

2 

2 

2 

3 

3 

015 

1413  1416 

1419 

1422 

1426 

1429 

1432 

1435 

1439 

1442 

0 

2 

2 

2 

3 

3 

0. 16 

1445  1449 

1452 

1455 

1459 

1462 

1466 

1469 

1472 

1476 

0 

2 

2 

2 

3 

3 

0.17 

147911483 

i486 

1489 

1493 

1496 

1500 

1503 

1507 

1510 

0 

2 

2 

2 

3 

3 

0.18 

151411517 

1521 

1524 

1528 

1531 

1535 

153S 

1542 

1545 

0 

2 

2 

2 

3 

3 

0.19 

1549 

1552 

1556 

1560 

1563 

1567 

1570 

1574 

1578 

1581 

c 

2 

2 

3 

3 

3 

0.20 

1585 

1589 

1592 

1596 

1600 

1603 

1607 

1611 

1614 

1618 

0 

I 

2 

2 

3 

3 

3 

0.21 

1622 

1626 

1629 

1633 

1637 

1641 

1644 

1648 

1652 

1656 

0 

2 

2 

2 

3 

3 

3 

0.22 

1660 

1663 

1667 

167I 

1675 

1679 

1683 

1687 

1690 

1694 

0 

2 

2 

2 

3 

3 

3 

0.23 

1698 

1702 

1706 

I7IO 

1714 

1718 

1722 

1726 

1730 

1734 

0 

■2 

2 

2 

3 

3 

4 

0.24 

1738 

1742 

1746 

1750 

1754 

1758 

1762 

1766 

1770 

1774 

0 

2 

2 

2 

3 

3 

4 

0.25 

1778 

1782 

1786 

179I 

1795 

1799 

1803 

1807 

1811 

1816 

0 

2 

2 

2 

3 

3 

4 

0.26 

1820 

1824 

1828 

1832 

1837 

1841 

1845 

1849 

1854 

1858 

0 

2 

2 

3 

3 

3 

4 

0.27 

1862 

1866 

1871 

1875 

1879 

1884 

1888 

1892 

1897 

1901 

0 

2 

2 

3 

3 

3 

4 

0.28 

1905 

1910 

1914 

I919 

1923 

1928 

1932 

1936 

1941 

1945 

0 

2 

2 

3 

3 

4 

4 

0.29 

1950 

1954 

1959 

1963 

1968 

1972 

1977 

1982 

1986 

1991 

0 

2 

2 

3 

3 

4 

4 

0.30 

1995 

2000 

2004 

2009 

2014 

2018 

2023 

2028 

2032 

2037 

0 

2 

2 

3 

3 

4 

4 

0.31 

2042 

2046 

2051 

2056 

2061 

2065 

2070 

2075 

2080 

2084 

0 

2 

2 

3 

3 

4 

4 

0.32 

2089  2094 

2099 

2104 

2109 

2113 

2118 

2123 

2128 

2133 

0 

2 

2 

3 

3 

4 

4 

0.33 

2138 

2143 

2148 

2153 

2158 

2163 

2168 

2173 

2178 

2183 

0 

2 

2 

3 

3 

4 

4 

0.34 

2188 

2193 

2198 

2203 

2208 

2213 

2218 

2223 

2228 

2234 

2 

2 

3 

3 

4 

4 

S 

0.35 

2239 

2244 

2249 

2254 

2259 

2265 

2270 

2275 

2280 

5286 

2 

2 

3 

3 

4 

4 

S 

0,36 

2291 

2296 

2301 

2307 

2312 

2317 

2323 

2328 

2333 

2339 

2 

2 

3 

3 

4 

4 

5 

0.37 

2344 

2350 

235s 

2360 

2366 

2371 

2377 

2382 

2388 

2393 

2 

2 

3 

3 

4 

4 

5 

0.38 

2399 

2404 

2410 

2415 

2421 

2427 

2432 

2438 

2443 

2449 

2 

2 

3 

3 

4 

4 

5 

0.39 

2455 

2460 

2466 

2472 

2477 

2483 

2489 

2495 

2500 

2506 

2 

2 

3 

3 

4 

5 

5 

0,40 

2512 

2518 

2523 

2529 

2535 

2541 

2547 

2553 

2559 

2564 

2 

2 

3 

4 

4 

5 

S 

0.41 

2570 

2576 

2582 

2588 

2594 

2600 

2606 

2612 

2618 

2624 

2 

2 

3 

4 

4 

5 

5 

0.42 

2630 

2636 

2642 

2649 

2655 

2661 

2667 

2673 

2679 

2685 

2 

2 

3 

4 

4 

5 

6 

0.43 

2692 

2698 

2704 

2710 

2716 

2723 

2729 

2735 

2742 

2748 

2 

3 

3 

4 

4 

5 

6 

0.44 

2754 

2761 

2767 

2773 

2780 

2786 

2793 

2799 

2805 

2812 

2 

3 

3 

4 

4 

S 

6 

0.45 

2818 

2825 

2831 

2838 

2844 

2851 

2858 

2864 

2871 

2877 

2 

3 

3 

4 

5 

S 

6 

0.46 

2884 

2891 

2897 

2904 

2911 

2917 

2924 

2931 

2938 

2944 

2 

3 

3 

4 

5 

s 

6 

0.47 

2951 

2958 

2965 

2972 

2979 

2985 

2992 

2999 

3006 

3013 

I 

2 

3 

3 

4 

5 

5 

6 

0.48 

3020 

3027 

3034 

3041 

3048 

3055 

3062 

3069 

3076 

3083 

2 

3 

4 

4 

S 

6 

6 

0.49 

3090 

3097 

3105 

3II2 

3"9 

3126 

3^33 

314I 

3H8 

3155 

2 

3 

4 

4 

5 

6 

6 

APPENDIX  A 
ANTILOGARITHMS 


227 


Loga- 

Proportional parts. 

rithms 

0 

I 

2 

3 

4 

5 

6 

7 

8    9   - 

I  2 

I  I 

3 

2 

4 
3 

5 

4 

6 

4 

7 
5 

8 

6 

9 

0.50 

5162 

3170 

3177 

3184 

3192 

3199 

3206 

3214 

3221 

3228 

7 

0-51 

3236 

3243 

3251 

3258 

3266 

3273 

3281 

3289 

3296 

3304 

I  2 

2 

3 

4 

5 

S 

6 

7 

0.52 

33^^ 

3319 

3327 

3334 

3342 

3350 

3357 

3365 

3373 

3381 

I  2 

2 

3 

4 

S 

S 

6 

7 

053 

3388 

3396 

3404 

3412 

3420 

3428 

3436 

3443 

3451 

3459 

I  2 

2 

3 

4 

S 

6 

6 

7 

0.54 

3467 

3475 

3483 

3491 

3499 

3508 

3516 

3524 

3532 

3540 

I  2 

2 

3 

4 

5 

6 

6 

7 

0.55 

3548 

3S5'J 

3565 

3573 

3581 

3589 

3597 

3606 

3614 

3622 

I  2 

2 

3 

4 

5 

6 

7 

7 

0.56 

3631 

3639 

3648 

3656 

3664 

3673  3681 

3690 

3698 

3707 

I  2 

3 

3 

4 

S 

6 

7 

8 

0.57 

3715 

3724 

3733 

3741 

3750 

3758 

3767 

3776 

3784 

3793 

I  2 

3 

3 

4 

5 

6 

7 

8 

0.58 

3802 

3811 

3819 

3828 

3837 

3846 

3855 

3864 

3873  3882 

I  2 

3 

4 

4 

5 

6 

7 

8 

0-59 

3890 

3899 

3908 

3917 

3926 

3936 

3945 

3954 

3963  3972 

I  2 

3 

4 

5 

5 

6 

7 

8 

0.60 

3981 

3990 

3999 

4009 

4018 

4027 

4036 

4046 

4055 

4064 

I  2 

3 

4 

S 

6 

6 

7 

8 

0.61 

4074 

4083 

4093 

4102 

4111 

4121 

4130 

4140 

4150 

4159 

I  2 

3 

4 

5 

6 

8 

9 

0.62 

4169 

4178 

4188 

4198 

4207 

4217 

4227 

4236 

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30 

APPENDIX  B 

REAGENTS 

Air  Analysis 

Pettenkofer  Method.  —  Barium  Hydroxide.  —  A  solution  con- 
taining about  4  grams  of  BaO  and  0.2  gram  of  BaCl2  to  the  liter, 
(i  c.c.  =  I  mg.  CO2,  approximately.): 

Sulphuric  Acid. — Dilute  45.45  c.c.  of  normal  sulphuric  acid 
to  one  Hter.  (i  c.c.  =  i  mg.  CO2.)  To  standardize  the  solu- 
tion measure  25  c.c.  into  a  weighed  platinum  dish,  add  dilute 
ammonia-water  in  slight  excess,  evaporate  to  dryness  on  the 
water-bath,  and  dry  at  120°  C.  to  constant  weight. 

Standard  Lime-water.  —  (For  Popular  Tests.)  —  Shake  one 
part  of  freshly  slaked  lime  with  20  parts  of  distilled  water  for 
twenty  minutes  and  let  the  solution  stand  overnight  or  until 
perfectly  clear.  This  solution  should  be  very  nearly  equiva- 
lent to  the  above  standard  sulphuric  acid.  To  a  liter  of 
distilled  water  add  2.5  c.c.  of  a  solution  of  0.7  gram  of  phenol- 
phthalein  in  100  c.c.  of  50  per  cent  alcohol  and  add  lime-water 
drop  by  drop  until  a  slight  permanent  pink  color  is  produced. 
Then  add  6.3  c.c.  of  the  above  calcium  hydroxide  solution.  The 
resulting  solution  is  the  standard  lime-water  used  for  the  tests. 

Water  Analysis 

For  Ammonia.  —  Water  Free  from  Ammonia.  —  The  ammonia- 
free  water  used  in  this  laboratory  is  made  by  redistilling  distilled 
water  from  a  solution  of  alkaline  permanganate  in  a  steam-heated 
copper  still.  Only  the  middle  portion  of  the  distillate  is  collected. 
Oftentimes  the  distillate  from  a  good  spring-water  may  be  used. 

Nessler's  Reagent.  —  Dissolve  61.750  grams  KI  in  250  c.c. 
distilled  water  and  add  a  cold  solution  of  HgCl2  which  has  been 
saturated  by  boiling  with  an  excess  of  the  salt  and  allowing  it 

228 


APPENDIX  229 

to  crystallize  out.  Add  the  HgClo  cautiously  until  a  slight  per- 
manent red  precipitate  (Hglo)  appears.  Dissolve  this  slight 
precipitate  by  adding  0.750  gram  powdered  KI.  Then  add 
150  grams  of  KOH  dissolved  in  250  c.c.  of  water.  Make  up  to 
a  liter  and  allow  it  to  stand  over  night  to  settle.  This  solution 
should  give  the  required  color  with  ammonia  within  five  minutes, 
and  should  not  precipitate  within  two  hours. 

Alkaline  Permanganate.  —  Dissolve  233  grams  of  the  best 
stick  potash  in  350  c.c.  of  distilled  water.  Filter  this  strong 
solution,  if  necessary,  through  a  layer  of  glass  wool  on  a  por- 
celain filter-plate.  Dilute  with  700  to  750  c.c.  of  distilled  water 
to  a  specific  gravity  of  1.125,  add  8  grams  of  potassium  per- 
manganate crystals,  and  boil  down  to  one  liter  to  free  the  solution 
from  nitrogen.  Each  new  lot  of  reagent  must  be  tested  before 
being  used,  but  when  the  chemicals  used  are  all  good  there 
should  be  no  correction  needed  for  ammonia  in  the  solution. 

Standard  Anwionia  Solution.  —  Dissolve  3.82  grams  chemi- 
cally pure  NH4CI  in  a  liter  of  water  free  from  ammonia.  This 
is  the  strong  solution  from  which  the  standard  solution  is 
made  by  diluting  10  c.c.  to  a  liter  with  water  free  from  am- 
monia. One  cubic  centimeter  of  the  standard  solution  = 
o.ooooi  gram  nitrogen.  This  solution,  like  the  nitrite  standard 
and  other  dilute  solutions,  must  be  preserved  in  sterilized  bot- 
tles protected  from  dust  and  organic  matter. 

For  Nitrites. — Standard  Nitrite  Solution.  —  The  pure  silver 
nitrite  used  in  making  this  solution  is  prepared  by  the  double 
decomposition  of  silver  nitrate  and  potassium  nitrite,  and  re- 
peated crystallizations  from  water  of  the  rather  difficultly  solu- 
ble silver  nitrite,  i.i  grams  of  this  silver  nitrite  are  dissolved 
in  nitrite-free  water,  the  silver  completely  precipitated  by  the 
addition  of  the  standard  salt  solution  used  in  the  determination 
of  chlorine,  and  the  solution  made  up  to  i  liter.  100  c.c.  of  this 
strong  solution  are  diluted  to  i  liter,  and  10  c.c.  of  this  last 
solution  again  diluted  to  i  liter.  The  final  solution  is  the  one 
used  in  preparing  standards,     i  c.c.  =  o.ooooooi  gram  nitrogen. 

Sulphanilic  Acid.  —  Dissolve   3.3    grams  sulphaniHc  acid  in 


230  APPENDIX 

750  c.c.  of  water  by  the  aid  of  heat,  and  add  250  c.c.  glacial 
acetic  acid. 

NapJdhylamine  Acetate.  —  Boil  0.5  gram  of  a-naphthylamine 
in  100  c.c.  of  water  in  a  small  Erlenmeyer  flask  for  about  five 
minutes,  filter  through  a  plug  of  washed  absorbent  cotton,  add 
250  c.c.  glacial  acetic  acid,  and  dilute  to  i  liter. 

For  Nitrates.  —  Standard  Nitrate  Solution.  —  Dissolve  0.720 
gram  of  pure  recrystallized  KNO3  in  i  liter  of  water.  Evapo- 
rate 10  c.c.  of  this  strong  solution  cautiously  on  the  watci-bath, 
moisten  quickly  and  thoroughly  with  2  c.c.  of  phenol-disul- 
phonic  acid,  and  dilute  to  i  liter  for  the  standard  solution. 
I  c.c.  —  o.oooooi  gram  nitrogen. 

Phenol-disulphonic  Acid. — Heat  together  3  grams  synthetic 
phenol  with  37  grams  pure,  concentrated  H2SO4  in  a  boiling 
water-bath  for  six  hours. 

Potassium  Hydroxide.  —  30  per  cent. 

For  Kjeldahl  Process.  —  Sulphuric  Acid.  —  Sp.  gr.  1.84. 
This  should  be  free  from  nitrogen.  May  be  obtained  from 
Baker  and  Adamson,  Easton,  Pa. 

Potassium  Hydroxide.  —  Dissolve  350  grams  of  the  best  stick 
potash  in  2.25  liters  of  water  and  boil  down  to  something  less 
than  a  liter  with  3  grams  of  permanganate  crystals.  When 
cold,  dilute  to  a  liter  with  water  free  from  ammonia. 

For  Chlorine.  —  Salt  Solution.  —  Dissolve  16.48  grams  of 
fused  NaCl  in  a  liter  of  distilled  water.  For  the  standard 
solution  dilute  100  c.c.  of  this  strong  solution  to  i  liter,  i  c.c.  = 
0.00 1  gram  chlorine. 

Silver  Nitrate.  —  Dissolve  about  2.42  grams  of  AgNOs  (dry 
crystals)  in  i  liter  of  chlorine-free  water,  i  c.c.  =  0.0005  gram 
CI,  approximately.     Standardize  against  the  NaCl  solution. 

Potassium  Chromate.  —  Dissolve  50  grams  neutral  K2Cr04  in 
a  little  distilled  water.  Add  enough  AgNOs  to  produce  a  slight 
red  precipitate.  Filter  and  make  the  filtrate  up  to  a  liter  with 
water  free  from  chlorine. 

Milk  of  Alumina  for  Decolorization. — Dissolve  125  grams  of 
potash  or  ammonia  alum  in  a  liter  of  distilled  water.     Pre- 


APPENDIX  231 

cipitate  the  A](0H)3  by  the  cautious  addition  of  XH4OH. 
Wash  the  precipitate  in  a  large  jar  by  decantation  until  free  from 
chlorine,  nitrites,  and  ammonia. 

For  Hardness.  —  Slandard  Calcium  Chloride  Solution.  —  Dis- 
solve 0.200  gram  of  pure  Iceland  spar  in  dilute  HCl,  taking  care 
to  avoid  loss  by  spattering,  and  evaporate  to  dryness  several 
times,  to  remove  the  excess  of  acid.  Dissolve  the  calcium 
chloride  thus  formed  in  i  liter  of  water. 

Slandard  Soap  Solution.  —  Dissolve  100  grams  of  the  best 
white,  dry  castile  soap  in  a  liter  of  80  per  cent  alcohol.  Of  this 
strong  solution  dissolve  75  to  100  c.c.  in  a  liter  of  70  per  cent 
alcohol.  This  solution  must  have  70  per  cent  alcohol  added  to 
it  until  14.25  c.c.  of  it  give  the  required  lather  with  50  c.c.  of 
the  above  CaClo  solution. 

Erythrosine  Indicator.  —  Dissolve  o.  i'  gram  of  ery throsine  in 
I  liter  of  water. 

Methyl  Orange  Indicator.  —  Dissolve  o.i  gram  Aniline  Orange, 
Merck,  (Methyl)  or  Orange  III  in  a  few  cubic  centimeters  of 
alcohol  and  dilute  to  100  c.c.  with  distilled  water. 

Soda  Reagent.  —  Equal  parts  of  sodium  hydroxide  and  sodium 

N 
carbonate  solutions,  the  mixture  to  be  approximately  — 

10 

For  Iron.  —  Standard  Solution. — Dissolve  0.7  gram  of  crys- 
tallized ferrous  ammonium  sulphate  in  50  c.c.  of  distilled  water 
and  add  20  c.c.  of  dilute  sulphuric  acid.  Warm  the  solution 
slightly  and  add  potassium  permanganate  until  the  iron  is  com- 
pletely oxidized.  Dilute  the  solution  to  one  liter.  One  cubic 
centimeter  of  the  standard  solution  equals  o.i  mg.  Fe. 

Potassium  Sulphocyanate.  —  20  grams  per  liter. 

Hydrochloric  Acid.  —  One  part  HCI  (sp.  gr.  1.20)  to  i  part  of 
water. 

Potassium  Permanganate.  —  Five  grams  K]\In04  in  i  liter  of 
water. 

For  Dissolved  Oxygen.  —  Manganous  Sulphate.  —  48  grams 
of  MnS04 .  4  HoO  in  100  c.c.  of  water. 

Alkaline  Potassium  Iodide.  —  360  grams  of  NaOH  and  100 
grams  of  KI  in  i  liter  of  water. 


232  APPENDIX 

Hydrochloric  Acid.  —  Sp.  gr.  1.20. 

Potassium  Acetate.  —  100  grams  in  100  c.c.  of  water. 

N 

Sodium  Thiosidphate  Solution. •     Dissolve  2.48  grams  of 

100 

the  pure  crystallized  salt  in  water  and  dilute  to  one  liter.     Stand- 

N 
ardize  against  a  - —  potassium  bichromate  solution. 
100 

For  Oxygen  Consumed.  — Standard  Ammonium  Oxalate  Solu- 
tion. —  Dissolve  0.888  gram  pure  ammonium  oxalate  in  i  liter 
of  distilled  water.  One  cubic  centimeter  is  equivalent  to  0.000 1 
gram  oxygen  consumed. 

Potassium  Permanganate  Solution.  —  Dissolve  0.4  gram  potas- 
sium permanganate  in  i  liter  of  distilled  water  and  standardize 
against  the  ammonium  oxalate  solution  according  to  the  method 
described  in  the  text. 

N 
For  Free  Carbonic   Acid.  —  Standard  —  Sodium  Carbonate 

22 

Solution. 

For  Lead.  —  Standard  Lead  Solution.  —  To  a  strong  solution  of 

lead  acetate  add  a  slight  excess  of  H2SO4,  filter  off  and  wash  the 

precipitate.     Dissolve  it  in  ammonium  acetate  solution,  made 

by  neutralizing  glacial  acetic  acid  with  strong  ammonia.     Make 

up  to  a  known  volume  and  determine  the  lead  in  an  aliquot 

part  by  precipitating  with  KoCr^Oy  and  weighing  the  lead  chro- 

mate.     Dilute  an  aliquot  part  to  make  a  convenient  standard, 

say  about  i  c.c.  =  o.ooi  gram  of  Pb. 

Food  Analysis 

Pumice.  —  Bits  of  ignited  pumice,  about  the  size  of  a  pea, 
dropped  while  hot  into  water  and  bottled  for  use. 

Alcohol  (for  Reichert-Meissl  method).  —  95  per  cent  alcohol 
redistilled  from  potassium  hydroxide. 

Iodine  Solution  (for  Hanus'  method) .  —  This  is  conveniently 
made  up  according  to  the  directions  of  Hunt.*  Dissolve  13.2 
grams  iodine  in  i  liter  of  glacial  acetic  acid  (99  per  cent,  show- 

*  J.  Soc.  Chem.  Ind.,  21,  1902,  454. 


APPENDIX  233 

ing  no  reduction  with  bichromate  and  sulphuric  acid) .  This  will 
best  be  done  by  adding  the  acetic  acid  in  portions  and  heating 
on  the  water-bath  with  frequent  shaking.  To  the  cold  solution 
add  enough  bromine  to  double  the  halogen  content,  as  shown 
by  titration.  Three  cubic  centimeters  of  bromine  is  sufficient. 
A  slight  excess  of  iodine  is  not  detrimental. 

Anhydrous  Ether. — Wash  ordinary  ether  several  times  with 
distilled  water  and  add  soUd  caustic  potash  until  most  of  the 
water  has  been  removed.  Then  add  small  pieces  of  clean 
metallic  sodium  until  there  is  no  further  evolution  of  hydrogen 
gas.  The  ether  thus  prepared  should  be  kept  over  metallic 
sodium  and  a  tube  of  calcium  chloride  should  be  inserted  in  the 
stopper,  in  order  to  allow  the  escape  of  any  accumulated  gas. 

Potassium  Sulphide.  —  Dissolve  40  grams  of  the  crystallized 
salt  in  I  liter  of  water  and  filter  through  glass  wool. 

Potassium  Hydroxide  (for  Kjeldahl  process).  —  Dissolve  700 
grams  of  the  best  quality  of  stick  potash  in  water  and  dilute  to 
I  liter. 

Basic  Lead  Acetate.  —  Boil  for  half  an  hour  440  grams  of  lead 
acetate  and  264  grams  of  litharge  in  1500  c.c.  of  water.  Cool 
and  dilute  to  2  liters.  Allow  to  settle  and  siphon  off  the  clear 
liquid.  (Specific  gravity  about  1.27,  containing  about  35  per 
cent  of  the  basic  salt.) 

Ferric  Alum.  —  Dissolve  2  grams  of  ferric  alum  in  100  c.c.  of 
water,  boil  the  solution  until  a  precipitate  appears,  and  filter. 

Fehlings  Solution.  —  {a)  Dissolve  69.28  grams  of  C.P.  crys- 
tallized copper  sulphate,  carefully  dried  between  blotting-paper, 
in  water  and  make  up  to  i  liter,  including  i  c.c.  of  strong  sul- 
phuric acid:  {h)  Dissolve  346  grams  of  sodium  potassium  tar- 
trate and  100  grams  of  sodium  hydroxide  in  water  and  make 
up  to  a  Hter. 


BIBLIOGRAPHY 

AIR 

The  following  list  contains  the  more  important  books  and 
articles  of  recent  publication. 

Barker,  A.  H.  The  Theory  and  Practice  of  Heating  and  Ventilation.  The 
Carton  Press,  London,  1912. 

Greene,  A.  M.  The  Elements  of  Heating  and  Ventilation.  John  Wiley  &  Sons, 
New  York,  1913. 

Hammarsten-Mandel.  a  Text  Book  of  Physiological  Chemistry.  John 
Wiley  &  Sons,  New  York,  1908. 

Hoffman,  J.  D.  Handbook  for  Heating  and  Ventilating  Engineers.  McGraw- 
Hill  Book  Co.,  New  York,  1913. 

Macfie,  Ronald  C.    Air  and  Health.    Methuen  &  Co.,  London,  1909. 

Richards,  Ellen  H.  Conservation  by  Sanitation.  John  Wiley  &  Sons,  New 
York,  191 1. 

Rosenau,  M.  J.     Preventive  Medicine  and  Hygiene.     Appleton,  New  York, 

1913- 

Shaw,  W.  W.  Air  Currents  and  the  Laws  of  Ventilation.  University  Press, 
Cambridge,  Eng.,  1907. 

SoPER,  J.  A.  Air  and  Ventilation  in  Subways.  John  Wiley  &  Sons,  New 
York,  1908. 

Talbot,  Marion.    House  Sanitation.     Whitcomb  &  Barrows,  Boston,  1913. 

Standard  Methods  for  the  Examination  of  Air.  American  Public  Health  Asso- 
ciation, Boston,  1910. 

Affleck.     Ventilation  of  Gymnasia.     Am.  Phys.  Ed.  Rev.,  1912. 

Air  Supply  and  Ventilation  Number.  Am.  J.  Pub.  Health,  Nov.,  1913,  3, 
pp. 1123-1210. 

Crowder.  a  Study  of  the  Ventilation  of  Sleeping  Cars.  Arch.  Intern.  Med., 
1911,  7,  pp.  85-133. 

Jordan  and  Carlson.  Ozone:  Its  Bactericidal,  Physiologic  and  Deodorizing 
Action.     J.  Am.  Med.  Assn.,  1913,  61,  p.  1007. 

McCuRDY.     Recirculated  Air.     Am.  Phys.  Ed.  Rev.,  1913,  Dec. 

Norton.  Ventilation  of  Sleeping  Cars.  Science  Conspectus,  191 2,  2,  pp. 
79-82. 

Transactions  of  the  15th  International  Congress  of  Hygiene  and  Demography. 
1913,  Vol.  2,  Pt.  II. 

Ventilation  Symposium.     J.  Ind.  Eng.  Chem.,  1914,  6,  p.  245. 

Vosmaer.     Industrial  Uses  of  Ozone.     J.  Ind.  Eng.  Chem.,  1914,  6,  p.  229. 

Winslow  &  Kligler.  a  Quantitative  Study  of  Bacteria  in  City  Dust.  Am. 
J.  Pub.  Health,  191 2,  2,  p.  663. 

234 


BIBLIOGRAPHY  235 

WATER 

The  following  list  contains  the  most  important  recent  books 
on  water,  from  a  sanitary  standpoint. 

Don,  J.  &  Chisholm,  J.  Modern  Methods  of  Water  Purification.  2nd  Ed., 
Longmans,  Green  &  Co.,  New  York,  1913. 

Fuller,  M.  L.  Domestic  Water  Supplies  for  the  Farm.  John  Wiley  &  Sons, 
New  York,  1912. 

Gerhard,  W.  P.  The  Sanitation,  Water  Supply  and  Sewage  Disposal  of 
Country  Houses.     D.  Van  Nostrand  Co.,  New  York,  1909. 

Hazen,  Allen.  The  Filtration  of  Public  Water  Supplies.  3rd  Ed.,  John 
Wiley  &  Sons,  New  York,  19 10. 

Hazen,  Allen.  Clean  Water  and  How  to  Get  It.  2nd  Ed.,  John  Wiley  & 
Sons,  New  York,  19 14. 

Mason,  W.  P.  Examination  of  Water.  4th  Ed.,  John  Wiley  &  Sons,  New 
York,  1912. 

Mason,  W.  P.    Water  Supply.     John  Wiley  &  Sons,  New  York,  1909. 

Prescott,  S.  C.  and  Winslow,  C.  E.  A.  Elements  of  Water  Bacteriology. 
3rd  Ed.,  John  Wiley  &  Sons,  New  York,  1913. 

RiDEAL,  S.     Water  and  Its  Purification.     Lockwood  &  Son,  London,  1902. 

Stocks,  H.  B.     Water  Analysis.     Griffin  &  Co.,  London,  1912. 

Thresh,  J.  C.  The  Examination  of  Waters  and  Water  Supplies.  2nd  Ed.,  P. 
Blackiston's  Son  &  Co.,  Philadelphia,  1913. 

Thresh,  J.  C.  A  Simple  Method  of  Water  Analysis.  7th  Ed.,  Churchill, 
London,  191 2. 

TiLLSMAN,  J.  Translation  by  H.  S.  Taylor.  Water  Purification  and  Sewage 
Disposal.     D.  Van  Nostrand  Co.,  New  York,  1913. 

Whlpple,  G.  C.  The  Microscopy  of  Drinking  Water.  3rd  Ed.,  John  Wiley 
&  Sons,  New  York,  1914. 

Whipple,  G.  C.  The  Value  of  Pure  Water.  John  Wiley  &  Sons,  New  York, 
1907. 

Annual  Reports,  Massachusetts  State  Board  of  Health,  1879  to  191 2. 

Reports  of  the  Metropolitan  Water  Board,  New  York  City. 

Reports  of  the  Royal  Commission  on  Sewage  Disposal,  England. 

FOOD 

Only  the  general  books  and  bulletins  published  since  1890 
which  are  most  available  to  the  student  are  given  here.  A  de- 
tailed list  of  all  important  references  to  food  will  be  found  at 
the  end  of  each  chapter  in  Leach's  Food  Inspection  and  Analysis. 

Allen,  A.  H.  Commercial  Organic  Analysis.  4th  Ed.,  Blakiston,  Phila., 
1911. 

Bailey,  E.  H.  S.  Sanitary  and  Applied  Chemistry.  Macmillan,  New  York, 
1906. 


236  BIBLIOGRAPHY 

Blyth,  a.  W.  and  M.  W.  Foods,  their  Composition  and  Analysis.  Griffin, 
London, 1909. 

Farrington,  E.  H.,  and  Woll,  F.  W.  Testing  Milk  and  Its  Products.  Men- 
dota  Book  Co.,  Madison,  Wis.,  1908. 

GiRARD,  C.  and  Dupre,  A.  Analyse  des  Matieres  Alimentaires.  2d  Ed., 
Dunod,  Paris,  1904. 

Hutchison,  R.     Food  and  Dietetics.     William  Wood,  New  York,  1908. 

KoNiG,  J.  Die  Menschlichen  Nahrungs  =  u.  Genussmittel.  Springer,  Berlin, 
1904. 

.     Die  Untersuchung  landwirtschaftlich  und  gewerblich  wichtiger  Sto£fe. 

Parey,  Berlin,  191 1. 

Leach,  A.  E.     Food  Inspection  and  Analysis.     Wiley,  New  York,  1909. 

Leffmann,  H.  and  Beam,  W.     Food  Analysis.     Blakiston,  Phila.,  1905. 

Lewkowitsch,  J.     Oils,  Fats  and  Waxes.     Macmillan,  New  York,  1909. 

Mitchell,  C.  A.     Flesh  Foods.     Griffin,  London,  1900. 

Moor,  C.  G.  Standards  for  Food  and  Drugs.  Bailliere,  Tindall  &  Co.x,  London, 
1902. 

Norton,  A.  P.  Food  and  Dietetics.  School  of  Home  Economics,  Chicago, 
1907. 

Olsen,  J.  C.     Pure  Food.     Ginn  &  Co.,  Boston,  191 1. 

Pearmain,  T.  H.,  and  Moor,  C.  G.  The  Analysis  of  Food  and  Drugs.  Bailliere, 
Tindall  &  Cox,  London,  1897. 

Richards,  E.  H.     The  Cost  of  Food.     Wiley,  New  York,  1901. 

.     Food  Materials  and  their  Adulterations.     Home  Science  Pub.   Co., 

Boston,  1908. 

Richmond,  H.  D.     Dairy  Chemistry.     London,  18S9. 

Rupp,  G.     Die  Untersuchung  von  Nahrungsmitteln.     Winter,  Heidelberg,  1900. 

Sherman,  H.  C.  Chemistry  of  Food  and  Nutrition.  Macmillan,  New  York, 
1911. 

.     Organic  Analysis.     Macmillan,  New  York,  191 2. 

Snyder,  H.     Human  Foods.     Macmillan,  New  York,  1908. 

Van  Slyke,  L.  L.  Testing  Milk  and  Milk  Products.  Orange  Judd,  New  York, 
1911. 

Wiley,  H.  W.  Principles  and  Practice  of  .Agricultural  Analysis.  Vol.  III. 
Chem.  Pub.  Co.,  Easton,  Pa.,  1S97. 

.     Foods  and  their  Adulteration.     Blakiston,  Phila.,  1911. 

The  following  bulletins  of  the  United  States  Department  of 
Agriculture  will  also  be  found  useful  for  study  or  reference  on 
the  general  question  of  food : 

Office  of  Experiment  Stations,  Bulletins 

No.      9.  Fermentations  of  Milk.     1892. 

ir.  Analyses  of  American  Feeding  Stuflfs.     1892. 

21.  Chemistry  and  Economy  of  Food.     1895. 

25.  Dairy  Bacteriology.     1895. 


BIBLIOGRAPHY  237 

28.  (Rev.  Ed.)  Chemical  Composition  of  American  Food  Materials.     1895. 

29.  Dietary  Studies  at  the  University  of  Tennessee.     1896. 

31.  Dietary  Studies  at  the  University  of  Missouri.     1896. 

32.  Dietary  Studies  at  Purdue  University.     1896. 

34.  Carbohydrates  of  Wheat,  Maize,  Flour,  and  Bread.     1896. 

35.  Food  and  Nutrition  Investigations  in  New  Jersey.     1896. 

37.  Dietary  Studies  at  the  Maine  State  College.     1897. 

38.  Dietary  Studies  —  Food  of  the  Negro  in  Alabama.     1897. 
40.   Dietary  Studies  in  New  Mexico.     1897. 

43.  Composition  and  Digestibility  of  Potatoes  and  Eggs.     1897. 

44.  Metabolism  of  Nitrogen  and  Carbon  in  the  Human  Organism.     1897. 

45.  A  Digest  of  Metabohsm  Experiments.     1897. 

46.  Dietary  Studies  in  New  York  City.     1898. 

52.  Nutrition  Investigations  in  Pittsburgh,  Pa.     1898. 

53.  Nutrition  Investigations  at  the  University  of  Tennessee.     1898. 

54.  Nutrition  Investigations  in  New  Mexico.     1898. 

55.  Dietary  Studies  in  Chicago.     1898.     . 

63.   Experiments  on  the  Conservation  of  Energy  in  the  Himian  Body. 
1899. 

66.  Creatin  and  Creatinin.     1899. 

67.  Bread  and  Bread  Making.     1899. 

69.  Experiments  on  the  Metabolism  of  Matter  and  Energy  in  the  Human 

Body.     1899. 

71.  Dietary  Studies  of  Negroes.     1899. 

75.  Dietar>'  Studies  of  University  Boat  Crews.     1900. 

84.  Nutrition  Investigations  at  the  California  Agr.  Expt.  Station.     1900. 

85.  Investigations  on  the  Digestibility  and  Nutritive  \'alue  of  Bread.     1900. 
89.  Effect  of  Muscular  Work  on  Digestion  of  Food  and  Metabolism  of 

Nitrogen.     1901. 
91.   Nutrition  Investigations  at  the  University  of  Illinois,  etc.     1901. 
98.   Effect  of  Severe  and  Prolonged  Muscular  Work  on  Food  Consumption 

Digestibility,  and  Metabolism.     1901. 

101.  Studies  on  Bread  and  Bread  IMaking.     1901. 

102.  Losses  in  Cooking  Meat.     1901. 

107.  Nutrition  Investigations  among  Fruitarians  and  Chinese.     1901. 

109.  Metabolism  of  IMatter  and  Energj-  in  the  Human  Body.     1902. 

1x6.  Dietary  Studies  in  New  York  City.     1902. 

117.  Effect  of  Muscular  Work  upon  Digestibility  of  Food  and  Metabolism 

of  Nitrogen.     1902. 

121.  Metabolism   of   Nitrogen,    Sulphur,    and    Phosphorus   in    the   Human 

Organism.     1902. 

126.  Digestibility  and  Nutritive  Value  of  Bread.     1903. 

129.  Dietary  Studies:   Boston  and  other  Places.     1903. 

132.  Further  Investigations  among  Fruitarians.     1903. 

152.  Dietary  Studies  with  Harvard  L^niversity  Students. 

162.  Studies  on  Influence  of  Cooking  on  Nutritive  Value  of  Meats. 

227.  Calcium,  Magnesium  and  Phosphorus  in  Food  and  Nutrition. 


238  BIBLIOGRAPHY 

Btireaii  of  Chemistry,  Bulletins 

No.    13.  Foods  and  Food  Adulteration  —  (Ten  Parts). 

45.  Analyses  of  Cereals. 

50.  Composition  of  Maize. 

59.  Composition  of  American  Wines. 

61.  Pure  Food  Laws  of  Foreign  Countries. 

66.  Fruits  and  Fruit  Products. 

69.  Foods  and  Food  Control. 

72.  American  Wines  at  Paris  Exposition  of  1900. 

77.  Olive  Oil  and  Its  Substitutes. 

84.  Influence  of  Food  Preservatives  and  Artificial  Colors  on  Digestion  and 

Health. 

100.  Some  Forms  of  Food  Adulteration  and  Simple  Methods  for  their  De- 
tection. 

107.  Official  and  Provisional  Methods  of  Analysis. 

no.  Chemical  Analysis  and  Composition  of  American  Honeys. 

114.  Meat  Extracts  and  Similar  Preparations. 

115.  Effects  of  Cold  Storage  on  Eggs,  Quail  and  Chickens. 

120.  Feeding  Value  of  Cereals. 

122.  Annual  Proceedings  A.  O.  A.  C. 

132.  Annual  Proceedings  A.  O.  A.  C. 

137.  Annual  Proceedings  A.  O.  A.  C.  ** 

152.  Annual  Proceedings  A.  O.  A.  C. 

162.  Annual  Proceedings  A.  O.  A.  C. 

164.  Graham  Flour. 

Fanners^  Bulletins 

No.    23.  Foods:   Nutritive  Value  and  Cost.     1894. 

29.  Souring  of  Milk.     1895. 

34.  Meats:   Composition  and  Cooking.     1896. 

74.  Milk  as  Food.     1898. 

85.  Fish  as  Food.     1898. 
93.  Sugar  as  Food.     1899. 

112.  Bread  and  the  Principles  of  Bread  Making.     1900. 

121.  Beans,  Peas,  and  other  Legumes  as  Food.     1900. 
128.  Eggs  and  their  Uses  as  Food.     1901. 

131.  Household  Tests  for  Detection  of  Oleomargarine  and  Renovated  Butter. 

190 1. 

142.  The  Nutritive  and  Economic  Value  of  Food.     1901. 

182.  Poultry  as  Food. 

249.  Cereal  Breakfast  Foods. 

252.  Maple  Sugar  and  Sirup. 

293.  Use  of  Fruit  as  Food. 

332.  Nuts  and  their  Uses  as  Food. 

363.  Use  of  Milk  as  Food. 

490.  Bacteria  in  Milk. 


BIBLIOGRAPHY  239 

Much  valuable  information  will  also  be  found  in  the  regular  bulletins  and  re- 
ports of  several  of  the  State  experiment  stations  and  boards  of  health,  notably 
those  of  Connecticut,  North  Dakota,  Maine,  Kansas,  New  Hampshire,  Vermont 
and  Massachusetts.  The  "Food  Inspection  Divisions"  and  "Notices  of  Judg- 
ment" issued  from  time  to  time  in  the  enforcement  of  the  Federal  Pure  Food 
Law  also  contain  interesting  information  concerning  the  adulteration  of  food. 


INDEX 


Pace 

Acid,  sulphanilic,  reagent 229 

sulphuric,  reagent  for  air  analysis 228 

Adams'  method  for  fat 141 

Adulteration,  cause  of 124 

character  of 128 

definition  of 1 24 

extent  of 128 

Air,  amount  of,  required 18 

bacteria  in 10,  42 

collection  of  samples  of 24 

composition  of  expired 11 

composition  of  inspired 9 

dust  in 9 

essential  to  life 2 

humidity  of 9,  14 

methods  of  analysis  of 21 

purification 20 

poisonous  gases  in 10 

Alcohol,  determination  of 191 

table 217 

Alkalinity,  determination  of,  in  water 92 

Alum,  determination  of,  in  water 95 

Alumina,  milk  of 230 

Ammonia,  albuminoid,  determination  of 72 

significance  of 61 

free,  determination  of 72 

significance  of 62 

free  water 228 

standard  solution  of 2  29 

Ammonium  oxalate  solution,  standard 232 

Analysis,  air,  methods  of 21 

water,  methods  of • 69 

accuracy  of  methods  of 59 

expression  of  results  of 5S 

interpretation  of  results  of 56 

Ash,  in  cereals iSo 

in  wine 193 

of  milk 141 

241 


242  INDEX 

Page 

Babcock  method  for  fat 142 

Bacteria  in  air, 10 

determination  of 42 

Barometers 21 

Basic  lead  acetate 233 

Beer,  analysis  of 197 

Benzoic  acid,  detection  of 196 

Bibliography 234 

Bleach,  use  of,  in  water  sterilization 54 

Boric  acid,  detection  in  milk 154 

Breakfast  foods 130 

Butter,  analysis  of 165 

composition  of 162 

Federal  standard  for 164 

microscopic  examination 178 

Butter-fat,  composition  of 163 

Calcium  chloride  solution,  standard 231 

Calorie,  definition  of 117 

Calorific  value 117 

Cane-sugar,  detection  in  milk 150 

Caramel  in  vanilla  extracts 204 

Carbohydrates,  function  of 115 

Carbon  dioxide,  allowable  amounts  in  air 17 

determination  of,  in  air 27 

in  water 84 

in  expired  air 11 

in  inspired  air 9 

poisonous  action  of 12 

table  of  weights  of  cubic  centimeters  of 209 

use  as  a  ventilation  test 17 

Carbon  monoxide  in  air 10 

determination  of 40 

Carbonaceous  matter  in  water,  determination  of 85 

Casein,  determination  in  milk 146 

Cereals,  analysis  of 180 

composition  of 181 

Chloride  of  lime,  use  in  water  sterilization 54 

Chlorides  in  water,  significance  of 64 

determination  of 84 

Chlorine,  map  of  normal 65 

in  water,  see  chlorides. 

Cholera 44 

Coal-tar  dyes,  detection  of 194 

Cohen  and  Appleyard  method  for  air  analysis 37 

Collection  of  samples  of  air 24 

water 69 


INDEX  243 

Pace 

Color  in  water,  determination  of 105 

Color,  detection  in  milk 154 

Colors  in  food 132 

Comfort II 

curve  of 16 

Cooking,  changes  caused  by 116 

Coumarin,  determination  of 201 

Crowd  poisoning,  theory  of 12 

Crude  fibre 188 

Dextrin,  determination  in  cereals 185 

Dietaries 1 20 

Dust  in  air g 

determination  of 23 

Electric  muflBe  furnace 88 

Erj'throsine  indicator 231 

Ether,  anhydrous 233 

extract  in  cereals 182 

Extract  in  beer-wort 222 

in  wine 192 

in  wine,  table 2  20 

Fat,  determination  in  milk 141 

in  cereals 182 

Fats,  function  of 114 

Fehlings'  solution 233 

Ferric  alum 233 

Ferrous  ammoniimi  sulphate,  standard  solution 89,  231 

Filter  galleries 50 

Filters,  water 52 

Filtration,  methods  of 52 

Fitz  shaker 39 

Food,  composition  of 112 

definition  and  uses iii 

essential  for  life 5 

materials,  composition  of iiS 

principles 112 

values,  discussion  of 122 

Foods,  predigested 120 

"Fore"  milk 13S 

Formaldehyde,  detection  in  milk 151 

Free  acids,  in  wine 193 

Gottlieb  method  for  fat 143 

Ground  waters 48 

Gunning  method 1 84 


244  INDEX 

Page 

Hale  and  IMelia  method  for  dissolved  oxygen loi 

Hanus  method 171 

Hardness,  acid  method  for 91 

permanent,  determination  of 93 

soap  method  for 90 

table  of 216 

temporary,  determination  of 92 

total,  determination  of 94 

Hazen's  theorem 45 

Heat  loss  from  the  body,  methods  of 13 

Heat  of  combustion 117 

Hehner  value 170 

Hehner's  acid  method  for  hardness 91 

Humidity 9 

determination  of 22 

effect  on  heat  loss  of 14 

table  of  relative 210 

Hygrometer,  hair 22 

Ice 55 

Imhoff  tank 61 

Indicator,  erythrosine 231 

methyl  orange 231 

potassium  chromate 84,  230 

Iodine  value 171 

Hanus  solution  for 232 

Iron  in  water,  determination  of 89 

standard  solution  of 231 

Jackson's  candle  turbidimeter 95 

Kjeldahl  method 183 

process  for  nitrogen  in  water 78 

reagents  for 230 

Kubel's  hot  acid  method 86 

Lead  in  water,  determination  of 97 

number  of  vanilla 202 

standard  solution  of 232 

Lemon  color 207 

extract 205 

oil,  determination  of 206 

Lime  water  reagent  for  air  analysis 38,  228 

Logwood  test  for  alum  in  water 95 

Loss  on  ignition,  determination  of,  in  water 87 

Low's  method  for  alum  in  water 96 


INDEX 


245 


Pace 

Malted  cereals,  analysis  of i8g 

Manganese  sulphate  solution 231 

Marsh  test  for  caramel 204 

Methyl  orange  indicator 231 

Milk,  composition  of 136 

detection  of  added  water 158 

interpretation  of  analysis 156 

serum,  examination  of 14Q 

solids,  calculation  of 148 

sugar,  determination  of 145 

variations  in  compositions  of 137 

Mills-Reincke  phenomenon 45 

Mineral  matter  in  water 65 

determination  of 87 

salts,  value  in  food 116 

Misbranding 125 

Moisture  in  cereals 180 

see  Humidity. 

Motion  of  air,  determination  of 22 

effect  on  heat  loss 14 

Naphthylamine  acetate  solution 80,  230 

Nessler  reagent 72,  228 

Nitrate  solution,  standard 230 

Nitrates  in  water,  determination  of 82 

significance  of 63 

Nitrite  solution,  standard 229 

Nitrites  in  air,  determination  of 42 

in  water,  determination  of 80 

significance  of 63 

Nitrogen  cycle 60 

in  water,  determination  of  total 78 

Nitrogen-free  extract 184 

Nitrogenous  substances,  function  of 113 

Nutritive  ratio 117 

Odor  in  water,  determination  of 106 

Odors  in  water,  extermination  of 48 

Oleomargarine 163 

Organic  matter  in  water 66 

determination  of 85 

Oxygen  consumed,  determination  of 85 

dissolved  in  water,  determination  of 100 

significance  of 66 

in  expired  air 1 1 

in  inspired  air q 

table  of  saturation  of  water  with 103 


246  INDEX 

Page 

Ozone,  use  in  purifying  air 20 

sterilizing  water 54 

Pettenkofer  method  for  carbon  dioxide ss 

Pettersen-Palmquist  apparatus 27 

Phcnoldisulphonic  acid  reagent 82,  230 

Pollution  in  wells,  methods  of  tracing 50 

past 63 

Potassium  acetate  solution 232 

chromate  indicator 230 

iodide  solution,  alkaline 231 

permanganate,  alkaline 73,  229 

permanganate  solution,  standard 232 

sulphocyanate  reagent 89,  23 1 

Preservatives,  detection  in  butter 166 

Preservatives  in  food 132 

Protein  by  Kjeldahl  method 182 

Proteins  in  milk 146 

Psychrometer 22 

Putrescibility  test 104 

Radiator,  platinum 88 

Rain  fall,  average 46 

water 45 

Rapid  methods  for  air  analysis 35 

Reagents  for  air  analysis 228 

water  analysis 228 

Reducing  sugar,  Munson  and  Walker's  table 221 

Refractive  index 173 

Refractometer 174 

principle  of 175 

Reichert-Meissl  number 167 

Renovated  butter,  manufacture  of 163 

Residue  on  evaporation,  determination  of 87 

Resins,  in  vanilla 203 

Respiration 11 

SalicyHc  acid,  detection  of 196 

Salt,  determination  in  butter 166 

Sanitary  science,  importance  of 2 

Sanitation,  scope  of  chemistry  of i 

Sediment,  determination  of 108 

Self-purification  of  streams 47 

Septic  tank 61 

Sewage  analysis 67,  109 

purification  required 44 

tables  of  analyses  of 213 


INDEX  247 

Pace 

Silver  nitrate  solution 84,  230 

Sl^immed  milk,  detection  of i6i 

Soap  method  for  hardness 90 

solution,  standard 231 

Soda  reagent 93,  231 

Sodium  carbonate,  detection  in  milk 154 

Sodium  chloride  solution,  standard 84,  230 

thiosulphate  solution,  standard 232 

Solids  of  milk 140 

Sonden  apparatus  for  air  analysis 27 

Specific  gravity  of  milk 139 

correction  table 216 

solids 162 

wine 191 

Spoon  test 177 

Standards  for  ammonia  determination 75,  77 

Starch,  determination  of 186 

Steam  vacuum  method  for  air  samples 25 

"  Strippings  " 138 

Sulphanilic  acid 80,  229 

Sulphates  in  water,  determination  of 95 

table  of 215 

Sulphites,  detection  of 198 

Sugars  in  cereal  products 185 

Surface  waters 46 

Temperature,  determination  of 21 

effect  on  heat  loss 13 

Tests  on  water,  value  of 67 

Thermometers,  wet  and  dry  bulb 22 

Turbidimeter  for  sulphates 95 

Turbidity,  determination  of 108 

Turmeric  in  lemon  extract 207 

Tj-phoid  fever 45 

Ultraviolet  light  for  water  sterilization 54 

Vanilla,  adulteration  of ^00 

determination  of 201 

extract 190 

Vapor  tension  of  water,  table  of 20S 

Ventilation 17 

formulae 18 

methods  of 19 

Volatile  acids,  in  wine i94 

Walker  method  for  carbon  dioxide -8 

Water,  analytical  methods 69 


248  INDEX 

Page 

Water,  bacteriological  examination  of 57,  109 

chemical  examination  of 59,  67 

consumption 43 

cycle  of 45 

daily  quantity  required 4 

ground 48 

need  of 3 

physiological  action  of 43 

purification  of 51 

rain 45 

relation  to  disease 44 

safe 56 

necessity  of 45 

samples,  collection  of 69 

sanitary  examination  of 57 

siphon  method 24 

sterilization  of 54 

storage  of 46 

supplies,  requirements  for 56 

surface 46 

vapor  in  air,  see  Humidity. 

waste 43 

Waters,  table  of  average  composition  of 211 

table  of  normal 212 

tables  of  polluted 213 

Wells,  deep 49 

shallow 49 

Wine,  composition  of 190 

Winkler  method  for  dissolved  oxygen 100 


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